All EyeLink Publications
All 12,000+ peer-reviewed EyeLink research publications up until 2023 (with some early 2024s) are listed below by year. You can search the publications library using keywords such as Visual Search, Smooth Pursuit, Parkinson’s, etc. You can also search for individual author names. Eye-tracking studies grouped by research area can be found on the solutions pages. If we missed any EyeLink eye-tracking papers, please email us!
2011 |
Anil Kumar; Irene Gottlob; Rebecca J. Mclean; Shery Thomas; Mervyn G. Thomas; Frank A. Proudlock Clinical and oculomotor characteristics of albinism compared to FRMD7 associated infantile nystagmus Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 5, pp. 2306–2313, 2011. @article{Kumar2011, PURPOSE. Previous studies have found no difference between nystagmus characteristics associated with idiopathic infantile nystagmus (IIN) and that associated with albinism. The present aim is to compare the oculomotor characteristics and other associated clinical features of albinism and a genetically homogenous group of IIN volunteers where the nystagmus is associated with FRMD7 mutations. METHODS. Oculomotor characteristics and related clinical features between albinism (n ⫽ 52) and idiopathic nystag- mus associated with FRMD7 mutations (FRMD7-IIN |
Ningdong Li; Xiajuan Wang; Yuchuan Wang; Liming Wang; Ming Ying; Ruifang Han; Yuyan Liu; Kanxing Zhao Investigation of the gene mutations in two Chinese families with X-linked infantile nystagmus Journal Article In: Molecular Vision, vol. 17, pp. 461–468, 2011. @article{Li2011, Purpose: To identify the gene mutations causing X-linked infantile nystagmus in two Chinese families (NYS003 and NYS008), of which the NYS003 family was assigned to the FERM domain–containing 7 (FRMD7) gene linked region in our previous study, and no mutations were found by direct sequencing. Methods: Two microsatellites, DXS1047 and DXS1001, were amplified using a PCR reaction for the linkage study in the NYS008 family. FRMD7 was sequenced and mutations were analyzed. Multiplex ligation-dependent probe amplification (MLPA) was used to detect FRMD7 mutations in the NYS003 family. Results: The NYS008 family yielded a maximum logarithm of odds (LOD) score of 1.91 at θ=0 with DXS1001. FRMD7 sequencing showed a nucleotide change of c. 623A>G in exon7 of the patients' FRMD7 gene, which was predicted to result in an H208R amino acid change. This novel mutation was absent in 100 normal Han Chinese controls. No FRMD7 gene mutations were detected by MLPA in the NYS003 family. Conclusions: We identified a novel mutation, c. 623A>G (p. H208R), in a Han Chinese family with infantile nystagmus. This mutation expands the mutation spectrum of FRMD7 and contributes to the research on the molecular pathogenesis of FRMD7. |
Xingshan Li; Pingping Liu; Keith Rayner Eye movement guidance in Chinese reading: Is there a preferred viewing location? Journal Article In: Vision Research, vol. 51, pp. 1146–1156, 2011. @article{Li2011a, In this study, we examined eye movement guidance in Chinese reading. We embedded either a 2-character word or a 4-character word in the same sentence frame, and observed the eye movements of Chinese readers when they read these sentences. We found that when all saccades into the target words were considered that readers eyes tended to land near the beginning of the word. However, we also found that Chinese readers' eyes landed at the center of words when they made only a single fixation on a word, and that they landed at the beginning of a word when they made more than one fixation on a word. However, simulations that we carried out suggest that these findings cannot be taken to unambiguously argue for word-based saccade targeting in Chinese reading. We discuss alternative accounts of eye guidance in Chinese reading and suggest that eye movement target planning for Chinese readers might involve a combination of character-based and word-based targeting contingent on word segmentation processes. |
Casimir J. H. Ludwig; J. Rhys Davies Estimating the growth of internal evidence guiding perceptual decisions Journal Article In: Cognitive Psychology, vol. 63, no. 2, pp. 61–92, 2011. @article{Ludwig2011, Perceptual decision-making is thought to involve a gradual accrual of noisy evidence. Temporal integration of the evidence reduces the relative contribution of dynamic internal noise to the decision variable, thereby boosting its signal-to-noise ratio. We aimed to estimate the internal evidence guiding perceptual decisions over time, using a novel combination of external noise and the response signal methods. Observers performed orientation discrimination of patterns presented in external noise. We varied the contrast of the patterns and the delay at which observers were forced to signal their decision. Each test stimulus (patterns and noise sample) was presented twice. Across two experiments we varied the avail- ability of the visual stimulus for processing. Observer model anal- yses of discrimination accuracy and response consistency to two passes of the same stimulus, suggested that there was very little growth in the internal evidence. The improvement in accuracy over time characterised by the speed-accuracy trade-off function pre- dominantly reflected a decreasing proportion of non-visual deci- sions, or pure guesses. There was no advantage to having the visual patterns visible for longer than 80 ms, indicating that only the visual information in a short window after display onset was used to drive the decisions. The remarkable constancy of the inter- nal evidence over time suggests that temporal integration of the sensory information was very limited. Alternatively, more extended integration of the evidence from memory could have taken place, provided that the dominant source of internal noise limiting performance occurs between-trials, which cannot be reduced by prolonged evidence integration. |
Arthur J. Lugtigheid; Eli Brenner; Andrew E. Welchman Speed judgments of three-dimensional motion incorporate extraretinal information Journal Article In: Journal of Vision, vol. 11, no. 13, pp. 1–11, 2011. @article{Lugtigheid2011, When tracking an object moving in depth, the visual system should take changes of eye vergence into account to judge the object's 3D speed correctly. Previous work has shown that extraretinal information about changes in eye vergence is exploited when judging the sign of 3D motion. Here, we ask whether extraretinal signals also affect judgments of 3D speed. Observers judged the speed of a small target surrounded by a large background. To manipulate extraretinal information, we varied the vergence demand of the entire stimulus sinusoidally over time. At different phases of vergence pursuit, we changed the disparity of the target relative to the background, leading observers to perceive approaching target motion. We determined psychometric functions for the target's approach speed when the eyes were (1) converging, (2) diverging, (3) maximally converged (near), and (4) maximally diverged (far). The target's motion was reported as faster during convergence and slower during divergence but perceived speed was little affected at near or far vergence positions. Thus, 3D speed judgments are affected by extraretinal signals about changes in eye rotation but appear unaffected by the absolute orientation of the eyes. We develop a model that accounts for observers' judgments by taking a weighted average of the retinal and extraretinal signals to target motion. |
Richard W. Hertle; Dongsheng Yang; Kenneth Adams; Roxanne Caterino Surgery for the treatment of vertical head posturing associated with infantile nystagmus syndrome: Results in 24 patients Journal Article In: Clinical and Experimental Ophthalmology, vol. 39, no. 1, pp. 37–46, 2011. @article{Hertle2011, Background: The study of the clinical and electrophysiological effects of eye muscle surgery on patients with infantile nystagmus has broadened our knowledge of the disease and its interventions. Design: Prospective, comparative, interventional case series. Participants: Twenty-four patients with a vertical head posture because of electrophysiologically diagnosed infantile nystagmus syndrome. The ages ranged from 2.5 to 38 years and follow up averaged 14.0 months. Methods: Thirteen patients with a chin-down posture had a bilateral superior rectus recession, inferior oblique myectomy and a horizontal rectus recession or tenotomy. Those 11 with a chin-up posture had a bilateral superior oblique tenectomy, inferior rectus recession and a horizontal rectus recession or tenotomy. Main Outcome Measures: Outcome measures included: demography, eye/systemic conditions and preoperative and postoperative; binocular, best optically corrected, null zone acuity, head posture, null zone foveation time and nystagmus waveform changes. Results: Associated conditions were strabismus in 66%, ametropia in 96%, amblyopia in 46% and optic nerve, foveal dysplasia or albinism in 54%. Null zone acuity increased at least 0.1 logMAR in 20 patients (P < 0.05 group mean change). Patients had significant (P < 0.05) improvements in degrees of head posture, average foveation time in milliseconds and infantile nystagmus syndrome waveform improvements. Conclusions: This study illustrates a successful surgical approach to treatment and provides expectations of ocular motor and visual results after vertical head posture surgery because of an eccentric gaze null in patients with infantile nystagmus syndrome. |
Arvid Herwig; Gernot Horstmann Action-effect associations revealed by eye movements Journal Article In: Psychonomic Bulletin & Review, vol. 18, no. 3, pp. 531–537, 2011. @article{Herwig2011, We move our eyes not only to get information, but also to supply information to our fellows. The latter eye movements can be considered as goal-directed actions to elicit changes in our counterparts. In two eye-tracking experiments, participants looked at neutral faces that changed facial expression 100 ms after the gaze fell upon them. We show that participants anticipate a change in facial expression and direct their first saccade more often to the mouth region of a neutral face about to change into a happy one and to the eyebrows region of a neutral face about to change into an angry expression. Moreover, saccades in response to facial expressions are initiated more quickly to the position where the expression was previously triggered. Saccade-effect associations are easily acquired and are used to guide the eyes if participants freely select where to look next (Experiment 1), but not if saccades are triggered by external stimuli (Experiment 2). |
Masahiro Hirai; Daniel R. Saunders; Nikolaus F. Troje Allocation of attention to biological motion: Local motion dominates global shape Journal Article In: Journal of Vision, vol. 11, no. 3, pp. 1–11, 2011. @article{Hirai2011, Directional information can be retrieved from a point-light walker (PLW) in two different ways: either from recovering the global shape of the articulated body or from signals in the local motion of individual dots. Here, we introduce a voluntary eye movement task to assess how the direction of a centrally presented, task-irrelevant PLW affects the onset latency and accuracy of saccades to peripheral targets. We then use this paradigm to design experiments to study which aspects of biological motion-the global form mediated by the motion of the walker or the local movements of critical features-drive the observed attentional effects. Putting the two cues into conflict, we show that saccade latency and accuracy were affected by the local motion of the dots representing the walker's feet-but only if they retain their familiar, predictable location within the display. |
Margit Höfler; Iain D. Gilchrist; Christof Körner Inhibition of return functions within but not across searches Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 5, pp. 1385–1397, 2011. @article{Hoefler2011, Inhibition of return (IOR) facilitates visual search by discouraging the reinspection of recently processed items. We investigated whether IOR operates across two consecutive searches of the same display for different targets. In Experiment 1, we demonstrated that IOR is present within each of the two searches. In Experiment 2, we found no evidence for IOR across searches. In Experiment 3, we showed that IOR is present across the two searches when the first search is interrupted, suggesting that the completion of the search is what causes the resetting of IOR. We concluded that IOR is a partially flexible process that can be reset when the task completes, but not necessarily when it changes. When resetting occurs, this flexibility ensures that the inhibition of previously visited locations does not interfere with the new search. |
Mackenzie G. Glaholt; Eyal M. Reingold Eye movement monitoring as a process tracing methodology in decision making research Journal Article In: Journal of Neuroscience, Psychology, and Economics, vol. 4, no. 2, pp. 125–146, 2011. @article{Glaholt2011, Over the past half century, research on human decision making has expanded from a purely behaviorist approach that focuses on decision outcomes, to include a more cognitive approach that focuses on the decision processes that occur prior to the response. This newer approach, known as process tracing, has employed various methods, such as verbal protocols, information search displays, and eye movement monitoring, to identify and track psychological events that occur prior to the response (such as cognitive states, stages, or processes). In the present article, we review empirical studies that have employed eye movement monitoring as a process tracing method in decision making research, and we examine the potential of eye movement monitoring as a process tracing methodology. We also present an experiment that further illustrates the experimental manipulations and analysis techniques that are possible with modern eye tracking technology. In this experiment, a gaze-contingent display was used to manipulate stimulus exposure during decision making, which allowed us to test a specific hypothesis about the role of eye movements in preference decisions (the Gaze Cascade model; Shimojo, Simion, Shimojo, & Scheier, 2003). The results of the experiment did not confirm the predictions of the Gaze Cascade model, but instead support the idea that eye movements in these decisions reflect the screening and evaluation of decision alternatives. In summary, we argue that eye movement monitoring is a valuable tool for capturing decision makers' information search behaviors, and that modern eye tracking technology is highly compatible with other process tracing methods such as retrospective verbal protocols and neuroimaging techniques, and hence it is poised to be an integral part of the next wave of decision research. |
Davis M. Glasser; James M. G. Tsui; Christopher C. Pack; Duje Tadin Perceptual and neural consequences of rapid motion adaptation Journal Article In: Proceedings of the National Academy of Sciences, vol. 108, no. 45, pp. E1080–E1088, 2011. @article{Glasser2011, Nervous systems adapt to the prevailing sensory environment, and the consequences of this adaptation can be observed in the responses of single neurons and in perception. Given the variety of timescales underlying events in the natural world, determining the temporal characteristics of adaptation is important to understanding how perception adjusts to its sensory environment. Previous work has shown that neural adaptation can occur on a timescale of milliseconds, but perceptual adaptation has generally been studied over relatively long timescales, typically on the order of seconds. This disparity raises important questions. Can perceptual adaptation be observed at brief, functionally relevant timescales? And if so, how do its properties relate to the rapid adaptation seen in cortical neurons? We address these questions in the context of visual motion processing, a perceptual modality characterized by rapid temporal dynamics. We demonstrate objectively that 25 ms of motion adaptation is sufficient to generate a motion aftereffect, an illusory sensation of movement experienced when a moving stimulus is replaced by a stationary pattern. This rapid adaptation occurs regardless of whether the adapting motion is perceived. In neurophysiological recordings from the middle temporal area of primate visual cortex, we find that brief motion adaptation evokes direction-selective responses to subsequently presented stationary stimuli. A simple model shows that these neural responses can explain the consequences of rapid perceptual adaptation. Overall, we show that the motion aftereffect is not merely an intriguing perceptual illusion, but rather a reflection of rapid neural and perceptual processes that can occur essentially every time we experience motion. |
Tamar H. Gollan; Timothy J. Slattery; Diane Goldenberg; Eva Van Assche; Wouter Duyck; Keith Rayner Frequency drives lexical access in reading but not in speaking: The frequency-lag hypothesis Journal Article In: Journal of Experimental Psychology: General, vol. 140, no. 2, pp. 186–209, 2011. @article{Gollan2011, To contrast mechanisms of lexical access in production versus comprehension we compared the effects of word frequency (high, low), context (none, low constraint, high constraint), and level of English proficiency (monolingual, Spanish-English bilingual, Dutch-English bilingual) on picture naming, lexical decision, and eye fixation times. Semantic constraint effects were larger in production than in reading. Frequency effects were larger in production than in reading without constraining context but larger in reading than in production with constraining context. Bilingual disadvantages were modulated by frequency in production but not in eye fixation times, were not smaller in low-constraint contexts, and were reduced by high-constraint contexts only in production and only at the lowest level of English proficiency. These results challenge existing accounts of bilingual disadvantages and reveal fundamentally different processes during lexical access across modalities, entailing a primarily semantically driven search in production but a frequency-driven search in comprehension. The apparently more interactive process in production than comprehension could simply reflect a greater number of frequency-sensitive processing stages in production. |
Timothy D. Hanks; Mark E. Mazurek; Roozbeh Kiani; Elisabeth Hopp; Michael N. Shadlen Elapsed decision time affects the weighting of prior probability in a perceptual decision task Journal Article In: Journal of Neuroscience, vol. 31, no. 17, pp. 6339–6352, 2011. @article{Hanks2011, Decisions are often based on a combination of new evidence with prior knowledge of the probable best choice. Optimal combination requires knowledge about the reliability of evidence, but in many realistic situations, this is unknown. Here we propose and test a novel theory: the brain exploits elapsed time during decision formation to combine sensory evidence with prior probability. Elapsed time is useful because (1) decisions that linger tend to arise from less reliable evidence, and (2) the expected accuracy at a given decision time depends on the reliability of the evidence gathered up to that point. These regularities allow the brain to combine prior information with sensory evidence by weighting the latter in accordance with reliability. To test this theory, we manipulated the prior probability of the rewarded choice while subjects performed a reaction-time discrimination of motion direction using a range of stimulus reliabilities that varied from trial to trial. The theory explains the effect of prior probability on choice and reaction time over a wide range of stimulus strengths. We found that prior probability was incorporated into the decision process as a dynamic bias signal that increases as a function of decision time. This bias signal depends on the speed-accuracy setting of human subjects, and it is reflected in the firing rates of neurons in the lateral intraparietal area (LIP) of rhesus monkeys performing this task. |
Till S. Hartmann; Frank Bremmer; Thomas D. Albright; Bart Krekelberg Receptive field positions in area MT during slow eye movements Journal Article In: Journal of Neuroscience, vol. 31, no. 29, pp. 10437–10444, 2011. @article{Hartmann2011, Perceptual stability requires the integration of information across eye movements. We first tested the hypothesis that motion signals are integrated by neurons whose receptive fields (RFs) do not move with the eye but stay fixed in the world. Specifically, we measured the RF properties of neurons in the middle temporal area (MT) of macaques (Macaca mulatta) during the slow phase of optokinetic nystagmus. Using a novel method to estimate RF locations for both spikes and local field potentials, we found that the location on the retina that changed spike rates or local field potentials did not change with eye position; RFs moved with the eye. Second, we tested the hypothesis that neurons link information across eye positions by remapping the retinal location of their RFs to future locations. To test this, we compared RF locations during leftward and rightward slow phases of optokinetic nystagmus. We found no evidence for remapping during slow eye movements; the RF location was not affected by eye-movement direction. Together, our results show that RFs of MT neurons and the aggregate activity reflected in local field potentials are yoked to the eye during slow eye movements. This implies that individual MT neurons do not integrate sensory information from a single position in the world across eye movements. Future research will have to determine whether such integration, and the construction of perceptual stability, takes place in the form of a distributed population code in eye-centered visual cortex or is deferred to downstream areas. |
Andreas Hartwig; W. Neil Charman; Hema Radhakrishnan Accommodative response to peripheral stimuli in myopes and emmetropes Journal Article In: Ophthalmic and Physiological Optics, vol. 31, no. 1, pp. 91–99, 2011. @article{Hartwig2011, Purpose: It has been suggested that peripheral refractive error may influence eye growth and the development of axial refractive error, implying that the peripheral retina is sensitive to defocus. This study aimed to evaluate the steady-state accommodative response to peripheral stimuli in 10 young, adult myopes (mean spherical equivalent error -2.10 ± 1.72 D, median -1.63 D, range -0.83 to -6.00 D) and 10 emmetropes (mean spherical equivalent error -0.02 ± 0.35 D, median +0.08 D, range -0.50 to +0.50 D). Methods: The subjects were asked to view monocularly the centre of a screen displaying each of a series of eccentric accommodative targets placed at 5, 10 and 15°. An axial target was viewed for comparison purposes. Accommodation was measured using an open-field autorefractor, each stimulus being varied between about 0 and 4 D with spherical trial lenses placed in front of the viewing eye. Results: The results confirm that the peripheral retina is sensitive to optical focus, up to field angles of at least 15°, with accommodative responses weakening as the peripheral angle increases. There is some evidence that peripheral accommodation may be less effective in myopes than emmetropes. Conclusions: Although peripheral accommodation can be demonstrated in the absence of a central stimulus, the accommodation response is normally dominated by the central stimulus and it seems unlikely that peripheral accommodation effects play an important role in refractive development. |
Andreas Hartwig; Emma Gowen; W. Neil Charman; Hema Radhakrishnan Working distance and eye and head movements during near work in myopes and non-myopes Journal Article In: Clinical and Experimental Optometry, vol. 94, no. 6, pp. 536–544, 2011. @article{Hartwig2011a, PURPOSE: Reasons for the development and progression of myopia remain unclear. Some studies show a high prevalence of myopia in certain occupational groups. This might imply that certain head and eye movements lead to ocular elongation, perhaps as a result of forces from the extraocular muscles, lids or other structures. The present study aims to analyse head and eye movements in myopes and non-myopes for near-vision tasks. METHODS: The study analysed head and eye movements in a cohort of 14 myopic and 16 non-myopic young adults. Eye and head movements were monitored by an eye tracker and a motion sensor while the subjects performed three near tasks, which included reading on a screen, reading a book and writing. Horizontal eye and head movements were measured in terms of angular amplitudes. Vertical eye and head movements were analysed in terms of the range of the whole movement during the recording. Values were also assessed as a ratio based on the width of the printed text, which changed between participants due to individual working distances. RESULTS: Horizontal eye and head movements were significantly different among the three tasks (p = 0.03 and p = 0.014, for eye and head movements, respectively, repeated measures ANOVA). Horizontal and vertical eye and head movements did not differ significantly between myopes and non-myopes. As expected, eye movements preponderated over head movements for all tasks and in both meridians. A positive correlation was found between mean spherical equivalent and the working distance for reading a book (r = 0.41; p = 0.025). CONCLUSIONS: The results show a similar pattern of eye movements in all participating subjects, although the amplitude of these movements varied considerably between the individuals. It is likely that some individuals when exposed to certain occupational tasks might show different eye and head movement patterns. |
Andreas Hartwig; Emma Gowen; W. Neil Charman; Hema Radhakrishnan Analysis of head position used by myopes and emmetropes when performing a near-vision reading task Journal Article In: Vision Research, vol. 51, no. 14, pp. 1712–1717, 2011. @article{Hartwig2011b, The aim of the study was to compare head posture in young, adult emmetropes and corrected myopes during a reading task. Thirty-two (32) myopes (mean spherical equivalent: -3.46 ± 2.35. D) and 22 emmetropes (mean spherical equivalent: -0.03 ± 0.36. D) participated in the study. Of the myopes, 16 were progressing (rate of progression ≥-0.5. D over the previous 2. years), 12 were stable (changes of -0.25. D or less over 2. years) and four could not be classified. Seated subjects were asked to read a text binocularly in their habitual posture. To measure head posture, two simultaneous images were recorded from different directions. In a separate study with the same subjects and conditions, a motion monitor was used to track head posture for 1. min. The habitual reading distance was measured in both studies, together with the stereoscopic acuity and fixation disparity for each subject.The results of the photographic study showed no significant differences in head posture or reading distance between the myopic and emmetropic groups (p>0.05) but there was some evidence that downward pitch angles were greater in progressing myopes than in non-progressing myopes (p=0.03). No correlations were observed between the binocular parameters and head posture. Reading distances were systematically shorter with the helmet-mounted eye tracker and it was concluded that posture was affected by the weight of the equipment. With this reservation, it appeared that the rate of change of downward pitch angle over the 1-min recording session increased with the subject's rate of myopia progression (correlation between myopia progression and slope of pitch: r2=-0.69 |
Ben M. Harvey; Serge O. Dumoulin In: Journal of Neuroscience, vol. 31, no. 38, pp. 13604–13612, 2011. @article{Harvey2011, Receptive field (RF) sizes and cortical magnification factor (CMF) are fundamental organization properties of the visual cortex. At increasing visual eccentricity, RF sizes increase and CMF decreases. A relationship between RF size and CMF suggests constancies in cortical architecture, as their product, the cortical representation of an RF (point image), may be constant. Previous animal neurophysiology studies of this question yield conflicting results. Here, we use fMRI to determine the relationship between the population RF (pRF) and CMF in humans. In average and individual data, the product of CMF and pRF size, the population point image, is near constant, decreasing slightly with eccentricity in V1. Interhemisphere and subject variations in CMF, pRF size, and V1 surface area are correlated, and the population point image varies less than these properties. These results suggest a V1 cortical processing architecture of approximately constant size between humans. Up the visual hierarchy, to V2, V3, hV4, and LO1, the population point image decreases with eccentricity, and both the absolute values and rate of change increase. PRF sizes increase between visual areas and with eccentricity, but when expressed in V1 cortical surface area (i.e., corticocortical pRFs), they are constant across eccentricity in V2/V3. Thus, V2/V3, and to some degree hV4, sample from a constant extent of V1. This may explain population point image changes in later areas. Consequently, the constant factor determining pRF size may not be the relationship to the local CMF, but rather pRF sizes and CMFs in visual areas from which the pRF samples. |
Katharina Havermann; Eckart Zimmermann; Markus Lappe Eye position effects in saccadic adaptation Journal Article In: Journal of Neurophysiology, vol. 106, no. 5, pp. 2536–2545, 2011. @article{Havermann2011, Saccades are used by the visual system to explore visual space with the high accuracy of the fovea. The visual error after the saccade is used to adapt the control of subsequent eye movements of the same amplitude and direction in order to keep saccades accurate. Saccadic adaptation is thus specific to saccade amplitude and direction. In the present study we show that saccadic adaptation is also specific to the initial position of the eye in the orbit. This is useful, because saccades are normally accompanied by head movements and the control of combined head and eye movements depends on eye position. Many parts of the saccadic system contain eye position information. Using the intrasaccadic target step paradigm, we adaptively reduced the amplitude of reactive saccades to a suddenly appearing target at a selective position of the eyes in the orbitae and tested the resulting amplitude changes for the same saccade vector at other starting positions. For central adaptation positions the saccade amplitude reduction transferred completely to eccentric starting positions. However, for adaptation at eccentric starting positions, there was a reduced transfer to saccades from central starting positions or from eccentric starting positions in the opposite hemifield. Thus eye position information modifies the transfer of saccadic amplitude changes in the adaptation of reactive saccades. A gain field mechanism may explain the eye position dependence found. |
Benjamin Y. Hayden; Sarah R. Heilbronner; John M. Pearson; Michael L. Platt Surprise signals in anterior cingulate cortex: Neuronal encoding of unsigned reward prediction errors driving adjustment in behavior Journal Article In: Journal of Neuroscience, vol. 31, no. 11, pp. 4178–4187, 2011. @article{Hayden2011, In attentional models of learning, associations between actions and subsequent rewards are stronger when outcomes are surprising, regardless of their valence. Despite the behavioral evidence that surprising outcomes drive learning, neural correlates of unsigned reward prediction errors remain elusive. Here we show that in a probabilistic choice task, trial-to-trial variations in preference track outcome surprisingness. Concordant with this behavioral pattern, responses of neurons in macaque (Macaca mulatta) dorsal anterior cingulate cortex (dACC) to both large and small rewards were enhanced when the outcome was surprising. Moreover, when, on some trials, probabilities were hidden, neuronal responses to rewards were reduced, consistent with the idea that the absence of clear expectations diminishes surprise. These patterns are inconsistent with the idea that dACC neurons track signed errors in reward prediction, as dopamine neurons do. Our results also indicate that dACC neurons do not signal conflict. In the context of other studies of dACC function, these results suggest a link between reward-related modulations in dACC activity and attention and motor control processes involved in behavioral adjustment. More speculatively, these data point to a harmonious integration between reward and learning accounts of ACC function on one hand, and attention and cognitive control accounts on the other. |
Benjamin Y. Hayden; John M. Pearson; Michael L. Platt Neuronal basis of sequential foraging decisions in a patchy environment Journal Article In: Nature Neuroscience, vol. 14, no. 7, pp. 933–939, 2011. @article{Hayden2011a, Deciding when to leave a depleting resource to exploit another is a fundamental problem for all decision makers. The neuronal mechanisms mediating patch-leaving decisions remain unknown. We found that neurons in primate (Macaca mulatta) dorsal anterior cingulate cortex, an area that is linked to reward monitoring and executive control, encode a decision variable signaling the relative value of leaving a depleting resource for a new one. Neurons fired during each sequential decision to stay in a patch and, for each travel time, these responses reached a fixed threshold for patch-leaving. Longer travel times reduced the gain of neural responses for choosing to stay in a patch and increased the firing rate threshold mandating patch-leaving. These modulations more closely matched behavioral decisions than any single task variable. These findings portend an understanding of the neural basis of foraging decisions and endorse the unification of theoretical and experimental work in ecology and neuroscience. |
N. Gorgoraptis; R. F. G. Catalao; Paul M. Bays; Masud Husain Dynamic updating of working memory resources for visual objects Journal Article In: Journal of Neuroscience, vol. 31, no. 23, pp. 8502–8511, 2011. @article{Gorgoraptis2011, Recent neurophysiological and imaging studies have investigated how neural representations underlying working memory (WM) are dynamically updated for objects presented sequentially. Although such studies implicate information encoded in oscillatory activity across distributed brain networks, interpretation of findings depends crucially on the underlying conceptual model of how memory resources are distributed. Here, we quantify the fidelity of human memory for sequences of colored stimuli of different orientation. The precision with which each orientation was recalled declined with increases in total memory load, but also depended on when in the sequence it appeared. When one item was prioritized, its recall was enhanced, but with corresponding decrements in precision for other objects. Comparison with the same number of items presented simultaneously revealed an additional performance cost for sequential display that could not be explained by temporal decay. Memory precision was lower for sequential compared with simultaneous presentation, even when each item in the sequence was presented at a different location. Importantly, stochastic modeling established this cost for sequential display was due to misbinding object features (color and orientation). These results support the view that WM resources can be dynamically and flexibly updated as new items have to be stored, but redistribution of resources with the addition of new items is associated with misbinding object features, providing important constraints and a framework for interpreting neural data. |
Dan J. Graham; Robert W. Jeffery Location, location, location: Eye-tracking evidence that consumers preferentially view prominently positioned nutrition information Journal Article In: Journal of the American Dietetic Association, vol. 111, no. 11, pp. 1704–1711, 2011. @article{Graham2011, Background: Nutrition Facts labels can keep consumers better informed about their diets' nutritional composition, however, consumers currently do not understand these labels well or use them often. Thus, modifying existing labels may benefit public health. Objective: The present study tracked the visual attention of individuals making simulated food-purchasing decisions to assess Nutrition Facts label viewing. Primary research questions were how self-reported viewing of Nutrition Facts labels and their components relates to measured viewing and whether locations of labels and specific label components relate to viewing. Design: The study involved a simulated grocery shopping exercise conducted on a computer equipped with an eye-tracking camera. A post-task survey assessed self-reported nutrition information viewing, health behaviors, and demographics. Subjects/setting: Individuals 18 years old and older and capable of reading English words on a computer (n=203) completed the 1-hour protocol at the University of Minnesota during Spring 2010. Statistical analyses: Primary analyses included X2, analysis of variance, and t tests comparing self-reported and measured viewing of label components in different presentation configurations. Results: Self-reported viewing of Nutrition Facts label components was higher than objectively measured viewing. Label components at the top of the label were viewed more than those at the bottom, and labels positioned in the center of the screen were viewed more than those located on the sides. Conclusions: Nutrition Facts label position within a viewing area and position of specific components on a label relate to viewing. Eye tracking is a valuable technology for evaluating consumers' attention to nutrition information, informing nutrition labeling policy (eg, front-of-pack labels), and designing labels that best support healthy dietary decisions. |
Sven-Thomas Graupner; Sebastian Pannasch; Boris M. Velichkovsky In: International Journal of Psychophysiology, vol. 80, no. 1, pp. 54–62, 2011. @article{Graupner2011, Attention, visual information processing, and oculomotor control are integrated functions of closely related brain mechanisms. Recently, it was shown that the processing of visual distractors appearing during a fixation is modulated by the amplitude of its preceding saccade (Pannasch & Velichkovsky, 2009). So far, this was demonstrated only at the behavioral level in terms of saccadic inhibition. The present study investigated distractor-related brain activity with cortical eye fixation-related potentials (EFRPs). Moreover, the following saccade was included as an additional classification criterion. Eye movements and EFRPs were recorded during free visual exploration of paintings. During some of the fixations, a visual distractor was shown as an annulus around the fixation position, 100. ms after the fixation onset. The saccadic context of a fixation was classified by its preceding and following saccade amplitudes with the cut-off criterion set to 4° of visual angle. The prolongation of fixation duration induced by distractors was largest for fixations preceded and followed by short saccades. EFRP data revealed a difference in distractor-related P2 amplitude between the saccadic context conditions, following the same trend as in eye movements. Furthermore, influences of the following saccade amplitude on the latency of the saccadic inhibition and on the N1 amplitude were found. The EFRP results cannot be explained by the influence of saccades per se since this bias was removed by subtracting the baseline from the distractor EFRP. Rather, the data suggest that saccadic context indicates differences in how information is processed within single visual fixations. |
Katherine Guérard; Jean Saint-Aubin; Pierre Boucher; Sébastien Tremblay The role of awareness in anticipation and recall performance in the hebb repetition paradigm: Implications for sequence learning Journal Article In: Memory & Cognition, vol. 39, no. 6, pp. 1012–1022, 2011. @article{Guerard2011, Sequence learning has notably been studied using the Hebb repetition paradigm (Hebb, 1961) and the serial reaction time (SRT) task (Nissen & Bullemer, Cognitive Psychology 19:1-32, 1987). These two paradigms produce robust learning effects but differ with regard to the role of awareness: Awareness does not affect learning a repeated sequence in the Hebb repetition paradigm, as is evidenced by recall performance, whereas in the SRT task, awareness helps to anticipate the location of the next stimulus. In this study, we examined the role of awareness in anticipation and recall performance, using the Hebb repetition paradigm. Eye movements were monitored during a spatial reconstruction task where participants had to memorize sequences of dot locations. One sequence was repeated every four trials. Results showed that recall performance for the repeated sequence improved across repetitions for all participants but that anticipation increased only for participants aware of the repetition. |
Xiao Gao; Quanchuan Wang; Todd Jackson; Guang Zhao; Yi Liang; Hong Chen Biases in orienting and maintenance of attention among weight dissatisfied women: An eye-movement study Journal Article In: Behaviour Research and Therapy, vol. 49, no. 4, pp. 252–259, 2011. @article{Gao2011, Despite evidence indicating fatness and thinness information are processed differently among weight-preoccupied and eating disordered individuals, the exact nature of these attentional biases is not clear. In this research, eye movement (EM) tracking assessed biases in specific component processes of visual attention (i.e., orientation, detection, maintenance and disengagement of gaze) in relation to body-related stimuli among 20 weight dissatisfied (WD) and 20 weight satisfied young women. Eye movements were recorded while participants completed a dot-probe task that featured fatness-neutral and thinness-neutral word pairs. Compared to controls, WD women were more likely to direct their initial gaze toward fatness words, had a shorter mean latency of first fixation on both fatness and thinness words, had longer first fixation on fatness words but shorter first fixation on thinness words, and shorter total gaze duration on thinness words. Reaction time data showed a maintenance bias towards fatness words among the WD women. In sum, results indicated WD women show initial orienting, speeded detection and initial maintenance biases towards fat body words in addition to a speeded detection - avoidance pattern of biases in relation to thin body words. In sum, results highlight the importance of the utility of EM-tracking as a means of identifying subtle attentional biases among weight dissatisfied women drawn from a non-clinical setting and the need to assess attentional biases as a dynamic process. |
Tyler W. Garaas; Marc Pomplun Distorted object perception following whole-field adaptation of saccadic eye movements Journal Article In: Journal of Vision, vol. 11, no. 1, pp. 1–11, 2011. @article{Garaas2011, The adaptation of an observer's saccadic eye movements to artificial post-saccadic visual error can lead to perceptual mislocalization of individual, transient visual stimuli. In this study, we demonstrate that simultaneous saccadic adaptation to a consistent error pattern across a large number of saccade vectors is accompanied by corresponding spatial distortions in the perception of persistent objects. To induce this adaptation, we artificially introduced several post-saccadic error patterns, which led to a systematic distortion in participants' oculomotor space and a corresponding distortion in their perception of the relative dimensions of a cross-figure. The results indicate a tight coupling between the oculomotor and visual-perceptual spaces that is not limited to misperception of individual visual locations but also affects metrics in the visual-perceptual space. This coupling suggests that our visual perception is continuously recalibrated by the post-saccadic error signal. |
Peggy Gerardin; Valérie Gaveau; Denis Pélisson; Claude Prablanc Integration of visual information for saccade production Journal Article In: Human Movement Science, vol. 30, no. 6, pp. 1009–1021, 2011. @article{Gerardin2011, To foveate a visual target, subjects usually execute a primary hypometric saccade (S1) bringing the target in perifoveal vision, followed by a corrective saccade (S2) or by more than one S2. It is still debated to what extent these S2 are pre-programmed or dependent only on post-saccadic retinal error. To answer this question, we used a visually-triggered saccade task in which target position and target visibility were manipulated. In one-third of the trials, the target was slightly displaced at S1 onset (so-called double step paradigm) and was maintained until the end of S1, until the start of the first S2 or until the end of the trial. Experiments took place in two visual environments: in the dark and in a dimly lit room with a visible random square background. The results showed that S2 were less accurate for shortest target durations. The duration of post-saccadic visual integration thus appears as the main factor responsible for corrective saccade accuracy. We also found that the visual context modulates primary saccade accuracy, especially for the most hypometric subjects. These findings suggest that the saccadic system is sensitive to the visual properties of the environment and uses different strategies to maintain final gaze accuracy. |
Taylor R. Hayes; Alexander A. Petrov; Per B. Sederberg A novel method for analyzing sequential eye movements reveals strategic influence on Raven's Advanced Progressive Matrices Journal Article In: Journal of Vision, vol. 11, no. 10, pp. 1–11, 2011. @article{Hayes2011, Eye movements are an important data source in vision science. However, the vast majority of eye movement studies ignore sequential information in the data and utilize only first-order statistics. Here, we present a novel application of a temporal-difference learning algorithm to construct a scanpath successor representation (SR; P. Dayan, 1993) that captures statistical regularities in temporally extended eye movement sequences. We demonstrate the effectiveness of the scanpath SR on eye movement data from participants solving items from Raven's Advanced Progressive Matrices Test. Analysis of the SRs revealed individual differences in scanning patterns captured by two principal components that predicted individual Raven scores much better than existing methods. These scanpath SR components were highly interpretable and provided new insight into the role of strategic processing on the Raven test. The success of the scanpath SR in terms of prediction and interpretability suggests that this method could prove useful in a much broader context. |
Becky Heaver; Samuel B. Hutton Keeping an eye on the truth? pupil size changes associated with recognition memory Journal Article In: Memory, vol. 19, no. 4, pp. 398–405, 2011. @article{Heaver2011, During recognition memory tests participants' pupils dilate more when they view old items compared to novel items. We sought to replicate this "pupil old/new effect" and to determine its relationship to participants' responses. We compared changes in pupil size during recognition when participants were given standard recognition memory instructions, instructions to feign amnesia, and instructions to report all items as new. Participants' pupils dilated more to old items compared to new items under all three instruction conditions. This finding suggests that the increase in pupil size that occurs when participants encounter previously studied items is not under conscious control. Given that pupil size can be reliably and simply measured, the pupil old/new effect may have potential in clinical settings as a means for determining whether patients are feigning memory loss. |
Sarah R. Heilbronner; Benjamin Y. Hayden; Michael L. Platt Decision salience signals in posterior cingulate cortex Journal Article In: Frontiers in Neuroscience, vol. 5, pp. 55, 2011. @article{Heilbronner2011, Despite its phylogenetic antiquity and clinical importance, the posterior cingulate cortex (CGp) remains an enigmatic nexus of attention, memory, motivation, and decision making. Here we show that CGp neurons track decision salience - the degree to which an option differs from a standard - but not the subjective value of a decision. To do this, we recorded the spiking activity of CGp neurons in monkeys choosing between options varying in reward-related risk, delay to reward, and social outcomes, each of which varied in level of decision salience. Firing rates were higher when monkeys chose the risky option, consistent with their risk-seeking preferences, but were also higher when monkeys chose the delayed and social options, contradicting their preferences. Thus, across decision contexts, neuronal activity was uncorrelated with how much monkeys valued a given option, as inferred from choice. Instead, neuronal activity signaled the deviation of the chosen option from the standard, independently of how it differed. The observed decision salience signals suggest a role for CGp in the flexible allocation of neural resources to motivationally significant information, akin to the role of attention in selective processing of sensory inputs. |
Stephen J. Heinen; Z. Jin; Scott N. J. Watamaniuk Flexibility of foveal attention during ocular pursuit Journal Article In: Journal of Vision, vol. 11, no. 2, pp. 1–12, 2011. @article{Heinen2011, Smooth pursuit of natural objects requires flexible allocation of attention to inspect features. However, it has been reported that attention is focused at the fovea during pursuit. We ask here if foveal attention is obligatory during pursuit, or if it can be disengaged. Observers tracked a stimulus composed of a central dot surrounded by four others and identified one of the dots when it dimmed. Extinguishing the center dot before the dimming improved task performance, suggesting that attention was released from it. To determine if the center dot automatically usurped attention, we provided the pursuit system with an alternative sensory signal by adding peripheral motion that moved with the stimulus. This also improved identification performance, evidence that a central target does not necessarily require attention during pursuit. Identification performance at the central dot also improved, suggesting that the spatial extent of the background did not attract attention to the periphery; instead, peripheral motion freed pursuit attention from the central dot, affording better identification performance. The results show that attention can be flexibly allocated during pursuit and imply that attention resources for pursuit of small and large objects come from different sources. |
Jennifer J. Heisz; Jennifer D. Ryan The effects of prior exposure on face processing in younger and older adults Journal Article In: Frontiers in Aging Neuroscience, vol. 3, pp. 15, 2011. @article{Heisz2011, Older adults differ from their younger counterparts in the way they view faces. We assessed whether older adults can use past experience to mitigate these typical face-processing differences; that is, we examined whether there are age-related differences in the use of memory to support current processing. Eye movements of older and younger adults were monitored as they viewed faces that varied in the type/amount of prior exposure. Prior exposure was manipulated by including famous and novel faces, and by presenting faces up to five times. We expected that older adults may have difficulty quickly establishing new representations to aid in the processing of recently presented faces, but would be able to invoke face representations that have been stored in memory long ago to aid in the processing of famous faces. Indeed, younger adults displayed effects of recent exposure with a decrease in the total fixations to the faces and a gradual increase in the proportion of fixations to the eyes. These effects of recent exposure were largely absent in older adults. In contrast, the effect of fame, revealed by a subtle increase in fixations to the inner features of famous compared to non-famous faces, was similar for younger and older adults. Our results suggest that older adults' current processing can benefit from lifetime experience, however the full benefit of recent experience on face processing is not realized in older adults. |
Maria J. S. Guerreiro; Pascal W. M. Van Gerven Now you see it, now you don't: Evidence for age-dependent and age-independent cross-modal distraction Journal Article In: Psychology and Aging, vol. 26, no. 2, pp. 415–426, 2011. @article{Guerreiro2011, Age-related deficits in selective attention have often been demonstrated in the visual modality and, to a lesser extent, in the auditory modality. In contrast, a mounting body of evidence has suggested that cross-modal selective attention is intact in aging, especially in visual tasks that require ignoring the auditory modality. Our goal in this study was to investigate age-related differences in the ability to ignore cross-modal auditory and visual distraction and to assess the role of cognitive control demands thereby. In a set of two experiments, 30 young (mean age = 23.3 years) and 30 older adults (mean age = 67.7 years) performed a visual and an auditory n-back task (0 ≤ n ≤ 2), with and without cross-modal distraction. The results show an asymmetry in cross-modal distraction as a function of sensory modality and age: Whereas auditory distraction did not disrupt performance on the visual task in either age group, visual distraction disrupted performance on the auditory task in both age groups. Most important, however, visual distraction was disproportionately larger in older adults. These results suggest that age-related distraction is modality dependent, such that suppression of cross-modal auditory distraction is preserved and suppression of cross-modal visual distraction is impaired in aging. |
Tuomo Häikiö; Raymond Bertram; Jukka Hyönä The development of whole-word representations in compound word processing: Evidence from eye fixation patterns of elementary school children Journal Article In: Applied Psycholinguistics, vol. 32, no. 3, pp. 533–551, 2011. @article{Haeikioe2011, The role of morphology in reading development was examined by measuring participants' eye movements while they read sentences containing either a hyphenated (e.g., ulko-ovi “front door”) or concatenated (e.g., autopeli “racing game”) compound. The participants were Finnish second, fourth, and sixth graders (aged 8, 10, and 12 years, respectively). Fast second graders and all four and sixth graders read concatenated compounds faster than hyphenated compounds. This suggests that they resort to slower morpheme-based processing for hyphenated compounds but prefer to process concatenated compounds via whole-word representations. In contrast, slow second graders' fixation durations were shorter for hyphenated than concatenated compounds. This implies that they process all compounds via constituent morphemes and that hyphenation comes to aid in this process. |
Antonio F. Macedo; Michael D. Crossland; Gary S. Rubin Investigating unstable fixation in patients with macular disease Journal Article In: Investigative Ophthalmology & Visual Science, vol. 52, no. 3, pp. 1275–1280, 2011. @article{Macedo2011, PURPOSE. To assess the effect on visual acuity of compensating fixation instability by controlling retinal image motion in people with macular disease. METHODS. Ten patients with macular disease participated in this study. Crowded and noncrowded visual acuity were measured using an eye tracking system to compensate for fixation instability. Four conditions, corresponding to four levels of retinal image motion, were tested: no compensation (normal motion), partial compensation (reduced motion), total compensation (no motion), and overcompensation (increased motion). Fixation stability and the number of preferred retinal loci were also measured. RESULTS. Modulating retinal image motion had the same effect on crowded and noncrowded visual acuity (P ⫽ 0.601). When fixation instability was overcompensated, acuity worsened by 0.1 logMAR units (P ⬍ 0.001) compared with baseline (no compensation) and remained equal to baseline for all other conditions. CONCLUSIONS. In people with macular disease, retinal image motion caused by fixation instability does not reduce either crowded or noncrowded visual acuity. Acuity declines when fixation instability is overcompensated, showing limited tolerance to increased retinal image motion. The results provide evidence that fixation instability does not improve visual acuity and may be a consequence of poor oculomotor control. |
Alexander Maier; Christopher J. Aura; David A. Leopold Infragranular sources of sustained local field potential responses in macaque primary visual cortex Journal Article In: Journal of Neuroscience, vol. 31, no. 6, pp. 1971–1980, 2011. @article{Maier2011, A local field potential (LFP) response can be measured throughout the visual cortex in response to the abrupt appearance of a visual stimulus. Averaging LFP responses to many stimulus presentations isolates transient, phase-locked components of the response that are consistent from trial to trial. However, stimulus responses are also composed of sustained components, which differ in their phase from trial to trial and therefore must be evaluated using other methods, such as computing the power of the response of each trial before averaging. Here, we investigate the basis of phase-locked and non-phase-locked LFP responses in the primary visual cortex of the macaque monkey using a novel variant of current source density (CSD) analysis. We applied a linear array of electrode contacts spanning the thickness of the cortex to measure the LFP and compute band-limited CSD power to identify the laminar sites of persistent current exchange that may be the basis of sustained visual LFP responses. In agreement with previous studies, we found a short-latency phase-locked current sink, thought to correspond to thalamocortical input to layer 4C. In addition, we found a prominent non-phase-locked component of the CSD that persisted as long as the stimulus was physically present. The latter was relatively broadband, lasted throughout the stimulus presentation, and was centered ∼500 μm deeper than the initial current sink. These findings demonstrate a fundamental difference in the neural mechanisms underlying the initial and sustained processing of simple visual stimuli in the V1 microcircuit. |
Femke Maij; Eli Brenner; Jeroen B. J. Smeets Temporal uncertainty separates flashes from their background during saccades Journal Article In: Journal of Neuroscience, vol. 31, no. 10, pp. 3708–3711, 2011. @article{Maij2011, It is known that spatial localization of flashed objects fails around the time of rapid eye movements (saccades). This mislocalization is often interpreted in terms of a combination of shifts and deformations of the brain's representation of space to account for the eye movement. Such temporary remapping of positions in space should affect all elements in a scene, leaving ordinal relationships between positions intact. We performed an experiment in which we presented flashes on a background with red and green regions to human subjects. We found that flashes that were presented on the green part of the background around the time of a saccade were readily reported to have been presented on the red part of the background and vice versa. This is inconsistent with the notion of a temporary shift and deformation of perceived space. To explain our results, we present a model that illustrates how temporal uncertainty could give rise to the observed spatial mislocalization. The model combines uncertainty about the time of the flash with a bias to localize targets where one is looking. It reproduced the pattern of mislocalization very accurately, showing that perisaccadic mislocalization can best be explained in terms of temporal uncertainty about the moment of the flash. |
Femke Maij; Eli Brenner; Jeroen B. J. Smeets Peri-saccadic mislocalization is not influenced by the predictability of the saccade target location Journal Article In: Vision Research, vol. 51, no. 1, pp. 154–159, 2011. @article{Maij2011a, Flashes presented around the time of a saccade are often mislocalized. The precise pattern of mislocalization is influenced by many factors. Here we study one such factor: the predictability of the saccade target's location. The experiment examines two conditions. In the first the subject makes the same horizontal rightward saccade to the same target location over and over again. In the second the subject makes saccades to a target that is jumping in unpredictable radial directions. A dot is flashed in the vicinity of the saccade target near the time of saccade onset. Subjects are asked to localize the flash by touching its location on the screen. Although various saccade parameters differed, the errors that subjects made were very similar in both conditions. We conclude that the pattern of mislocalization does not depend on the predictability of the location of the saccade target. |
Alexis D. J. Makin; Rochelle Ackerley; Kelly S. Wild; Ellen Poliakoff; Emma Gowen; Wael El-Deredy Coherent illusory contours reduce microsaccade frequency Journal Article In: Neuropsychologia, vol. 49, no. 9, pp. 2798–2801, 2011. @article{Makin2011, Synchronized high-frequency gamma band oscillations (30-100. Hz) are thought to mediate the binding of single visual features into whole-object representations. For example, induced gamma band oscillations (iGBRs) have been recorded ∼280. ms after the onset of a coherent Kanizsa triangle, but not after an incoherent equivalent shape. However, several recent studies have provided evidence that the EEG-recorded iGBR may be a by-product of small saccadic eye movements (microsaccades). Considering these two previous findings, one would hypothesis that there should be more microsaccades following the onset of a coherent Kanizsa triangle. However, we found that microsaccade rebound rate was significantly higher after an incoherent triangle was presented. This result suggests that microsaccades are not a reliable indicator of perceptual binding, and, more importantly, implies that iGBR cannot be universally produced by ocular artefacts. |
Mauro Marchitto; Leandro Luigi Di Stasi; José J. Cañas Ocular movements under taskload manipulations: Influence of geometry on saccades in air traffic control simulated tasks Journal Article In: Human Factors and Ergonomics in Manufacturing & Service Industries, vol. 19, no. 6, pp. 1–13, 2011. @article{Marchitto2011, Traffic geometry is a factor that contributes to cognitive complexity in air traffic control. In conflict-detection tasks, geometry can affect the attentional effort necessary to correctly perceive and interpret the situation; online measures of situational workload are therefore highly desirable. In this study, we explored whether saccadic movements vary with changes in geometry. We created simple scenarios with two aircraft and simulated a conflict detection task. Independent variables were the conflict angle and the distance to convergence point. We hypothesized lower saccadic peak velocity (and longer duration) for increasing complexity, that is, for increasing conflict angles and for different distances to convergence point. Response times varied accordingly with task complexity. Concerning saccades, there was a decrease of peak velocity (and a related increase of duration) for increased geometry complexity for large saccades (>15°). The data therefore suggest that geometry is able to influence "reaching" saccades and not "fixation" saccades. |
Andrea E. Martin; Brian McElree Direct-access retrieval during sentence comprehension: Evidence from Sluicing Journal Article In: Journal of Memory and Language, vol. 64, no. 4, pp. 327–343, 2011. @article{Martin2011, Language comprehension requires recovering meaning from linguistic form, even when the mapping between the two is indirect. A canonical example is ellipsis, the omission of information that is subsequently understood without being overtly pronounced. Comprehension of ellipsis requires retrieval of an antecedent from memory, without prior prediction, a property which enables the study of retrieval in situ (Martin & McElree, 2008, 2009). Sluicing, or inflectional-phrase ellipsis, in the presence of a conjunction, presents a test case where a competing antecedent position is syntactically licensed, in contrast with most cases of nonadjacent dependency, including verb-phrase ellipsis. We present speed-accuracy tradeoff and eye-movement data inconsistent with the hypothesis that retrieval is accomplished via a syntactically guided search, a particular variant of search not examined in past research. The observed timecourse profiles are consistent with the hypothesis that antecedents are retrieved via a cue-dependent direct-access mechanism susceptible to general memory variables. |
Jessica Maryott; Abigail L. Noyce; Robert Sekuler Eye movements and imitation learning: Intentional disruption of expectation Journal Article In: Journal of Vision, vol. 11, no. 1, pp. 1–16, 2011. @article{Maryott2011, Over repeated viewings of motion along a quasi-random path, ability to reproduce that path from memory improves. To assess the role of expectations and sequence context on such learning, subjects eye movements were measured while trajectories were viewed for subsequent reproduction. As a sequence of motions was repeated, subjects' eye movements became anticipatory, leading the stimulus' motions. To investigate how prediction errors affected eye movements and imitation learning, we injected an occasional deviant motion into a well-learned stimulus sequence, violating subjects' expectation about the motion that would be seen. This unexpected direction of motion in the stimulus sequence did not impair reproduction of the sequence. The externally induced prediction errors promoted one-shot learning: During the very next stimulus presentation, their eye movements showed that subjects now expected the new sequence item to reappear. A second experiment showed that an associative mismatch can facilitate accurate reproduction of an unexpected stimulus. After a deviant sequence item was presented, imitation accuracy for sequences that contained the deviant direction of motion was reduced relative to sequences that restored the original direction of motions. These findings demonstrate that in the context of a familiar sequence, unexpected events can play an important role in learning the sequence. |
Kazunaga Matsuki; Tracy Chow; Mary Hare; Jeffrey L. Elman; Christoph Scheepers; Ken McRae Event-based plausibility immediately influences on-line language comprehension Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 37, no. 4, pp. 913–934, 2011. @article{Matsuki2011, In some theories of sentence comprehension, linguistically relevant lexical knowledge, such as selectional restrictions, is privileged in terms of the time-course of its access and influence. We examined whether event knowledge computed by combining multiple concepts can rapidly influence language understanding even in the absence of selectional restriction violations. Specifically, we investigated whether instruments can combine with actions to influence comprehension of ensuing patients of (as in Rayner, Warren, Juhuasz, & Liversedge, 2004; Warren & McConnell, 2007). Instrument-verb-patient triplets were created in a norming study designed to tap directly into event knowledge. In self-paced reading (Experiment 1), participants were faster to read patient nouns, such as hair, when they were typical of the instrument-action pair (Donna used the shampoo to wash vs. the hose to wash). Experiment 2 showed that these results were not due to direct instrument-patient relations. Experiment 3 replicated Experiment 1 using eyetracking, with effects of event typicality observed in first fixation and gaze durations on the patient noun. This research demonstrates that conceptual event-based expectations are computed and used rapidly and dynamically during on-line language comprehension. We discuss relationships among plausibility and predictability, as well as their implications. We conclude that selectional restrictions may be best considered as event-based conceptual knowledge rather than lexical-grammatical knowledge. |
Elmar H. Pinkhardt; Jan Kassubek Ocular motor abnormalities in Parkinsonian syndromes Journal Article In: Parkinsonism and Related Disorders, vol. 17, no. 4, pp. 223–230, 2011. @article{Pinkhardt2011, Oculomotor abnormalities can be observed in all Parkinsonian syndromes (PS). Nevertheless, due to the considerable overlap of oculomotor pathology in Parkinsonism, oculomotor changes are not generally considered to contribute substantially to the differential diagnosis of PS. Here we review the characteristics of oculomotor disturbances in the major PS, we provide a survey of the current concepts of the underlying neural physiology of oculomotor control and a summary of the major recording techniques for eye movements. The main focus of this review is to outline the subtle differences between apparently similar oculomotor alterations in Parkinson's disease (PD) and atypical neurodegenerative PS that can contribute to the early differential diagnosis of these entities. |
L. Pisella; N. Alahyane; A. Blangero; F. Thery; S. Blanc; Denis Pelisson Right-hemispheric dominance for visual remapping in humans Journal Article In: Philosophical Transactions of the Royal Society B: Biological Sciences, vol. 366, pp. 572–585, 2011. @article{Pisella2011, We review evidence showing a right-hemispheric dominance for visuo-spatial processing and representation in humans. Accordingly, visual disorganization symptoms (intuitively related to remapping impairments) are observed in both neglect and constructional apraxia. More specifically, we review findings from the intervening saccade paradigm in humans–and present additional original data–which suggest a specific role of the asymmetrical network at the temporo-parietal junction (TPJ) in the right hemisphere in visual remapping: following damage to the right dorsal posterior parietal cortex (PPC) as well as part of the corpus callosum connecting the PPC to the frontal lobes, patient OK in a double-step saccadic task exhibited an impairment when the second saccade had to be directed rightward. This singular and lateralized deficit cannot result solely from the patient's cortical lesion and, therefore, we propose that it is due to his callosal lesion that may specifically interrupt the interhemispheric transfer of information necessary to execute accurate rightward saccades towards a remapped target location. This suggests a specialized right-hemispheric network for visuo-spatial remapping that subsequently transfers target location information to downstream planning regions, which are symmetrically organized. |
Alexander Pollatsek; Raymond Bertram; Jukka Hyönä Processing novel and lexicalised Finnish compound words Journal Article In: Journal of Cognitive Psychology, vol. 23, no. 7, pp. 795–810, 2011. @article{Pollatsek2011, Participants read sentences in which novel and lexicalized two-constituent compound words appeared while their eye movements were measured. The frequency of the first constituent of the compounds was also varied factorially and the frequency of the lexicalized compounds was equated over the two conditions. The sentence frames prior to the target word were matched across conditions. Both lexicality and first constituent frequency had large and significant effects on gaze durations on the target word; moreover the constituent frequency effect was significantly larger for the novel words. These results indicate that first constituent frequency has an effect in two stages: in the initial encoding of the compound and in the construction of meaning for the novel compound. The difference between this pattern of results and those for English prefixed words (Pollatsek, Slattery, & Juhasz, 2008) is apparently due to differences in the construction of meaning stage. A general model of the relationship of the processing of polymorphemic words to how they are fixated is presented. |
Michi Matsukura; James R. Brockmole; Walter R. Boot; John M. Henderson Oculomotor capture during real-world scene viewing depends on cognitive load Journal Article In: Vision Research, vol. 51, no. 6, pp. 546–552, 2011. @article{Matsukura2011, It has been claimed that gaze control during scene viewing is largely governed by stimulus-driven, bottom-up selection mechanisms. Recent research, however, has strongly suggested that observers' top-down control plays a dominant role in attentional prioritization in scenes. A notable exception to this strong top-down control is oculomotor capture, where visual transients in a scene draw the eyes. One way to test whether oculomotor capture during scene viewing is independent of an observer's top-down goal setting is to reduce observers' cognitive resource availability. In the present study, we examined whether increasing observers' cognitive load influences the frequency and speed of oculomotor capture during scene viewing. In Experiment 1, we tested whether increasing observers' cognitive load modulates the degree of oculomotor capture by a new object suddenly appeared in a scene. Similarly, in Experiment 2, we tested whether increasing observers' cognitive load modulates the degree of oculomotor capture by an object's color change. In both experiments, the degree of oculomotor capture decreased as observers' cognitive resources were reduced. These results suggest that oculomotor capture during scene viewing is dependent on observers' top-down selection mechanisms. |
Hideyuki Matsumoto; Yasuo Terao; Toshiaki Furubayashi; Akihiro Yugeta; Hideki Fukuda; Masaki Emoto; Ritsuko Hanajima; Yoshikazu Ugawa Small saccades restrict visual scanning area in Parkinson's disease Journal Article In: Movement Disorders, vol. 26, no. 9, pp. 1619–1626, 2011. @article{Matsumoto2011, The purpose of this study wasto investigate abnormalities in visual scanning when Parkinson's disease patients view images of varying complexity. Eighteen nondemented Parkinson's disease patients and 18 normal subjects participated in the study. The ocular fixation position during viewing visual images was recorded using an eye-tracking device. The number of saccades, duration of fixation, amplitude of saccades, and scanned area in Parkinson's disease patients were compared with those in normal subjects. We also investigated whether the number of saccades, duration of fixation, or amplitude of saccades influenced the scanned area. While scanning images of varying complexity, Parkinson's disease patients made fewer saccades with smaller amplitude and longer fixation compared with normal subjects. As image complexity increased, the number of saccades and duration of fixation gradually approached those of normal subjects. Nevertheless, the scanned area in Parkinson's disease patients was consistently smaller than that in normal subjects. The scanned area significantly correlated with saccade amplitude in most images. Importantly, although Parkinson's disease patients cannot make frequent saccades when viewing simple figures, they can increase the saccade number and reduce their fixation duration when viewing more complex figures, making use of the abundant visual cues in such figures, suggesting the existence of ocular kinesie paradoxale. Nevertheless, both the saccade amplitude and the scanned area were consistently smaller than those of normal subjects for all levels of visual complexity. This indicates that small saccade amplitude is the main cause of impaired visual scanning in Parkinson's disease patients. |
Hideyuki Matsumoto; Yasuo Terao; Akihiro Yugeta; Hideki Fukuda; Masaki Emoto; Toshiaki Furubayashi; Tomoko Okano; Ritsuko Hanajima; Yoshikazu Ugawa Where do neurologists look when viewing brain CT images? An eye-tracking study involving stroke cases Journal Article In: PLoS ONE, vol. 6, no. 12, pp. e28928, 2011. @article{Matsumoto2011a, The aim of this study was to investigate where neurologists look when they view brain computed tomography (CT) images and to evaluate how they deploy their visual attention by comparing their gaze distribution with saliency maps. Brain CT images showing cerebrovascular accidents were presented to 12 neurologists and 12 control subjects. The subjects' ocular fixation positions were recorded using an eye-tracking device (Eyelink 1000). Heat maps were created based on the eye-fixation patterns of each group and compared between the two groups. The heat maps revealed that the areas on which control subjects frequently fixated often coincided with areas identified as outstanding in saliency maps, while the areas on which neurologists frequently fixated often did not. Dwell time in regions of interest (ROI) was likewise compared between the two groups, revealing that, although dwell time on large lesions was not different between the two groups, dwell time in clinically important areas with low salience was longer in neurologists than in controls. Therefore it appears that neurologists intentionally scan clinically important areas when reading brain CT images showing cerebrovascular accidents. Both neurologists and control subjects used the "bottom-up salience" form of visual attention, although the neurologists more effectively used the "top-down instruction" form. |
Ali Mazaheri; Nicholas E. DiQuattro; Jesse Bengson; Joy J. Geng Pre-stimulus activity predicts the winner of top-down vs. bottom-up attentional selection Journal Article In: PLoS ONE, vol. 6, no. 2, pp. e16243, 2011. @article{Mazaheri2011, Our ability to process visual information is fundamentally limited. This leads to competition between sensory information that is relevant for top-down goals and sensory information that is perceptually salient, but task-irrelevant. The aim of the present study was to identify, from EEG recordings, pre-stimulus and pre-saccadic neural activity that could predict whether top-down or bottom-up processes would win the competition for attention on a trial-by-trial basis. We employed a visual search paradigm in which a lateralized low contrast target appeared alone, or with a low (i.e., non-salient) or high contrast (i.e., salient) distractor. Trials with a salient distractor were of primary interest due to the strong competition between top-down knowledge and bottom-up attentional capture. Our results demonstrated that 1) in the 1-sec pre-stimulus interval, frontal alpha (8-12 Hz) activity was higher on trials where the salient distractor captured attention and the first saccade (bottom-up win); and 2) there was a transient pre-saccadic increase in posterior-parietal alpha (7-8 Hz) activity on trials where the first saccade went to the target (top-down win). We propose that the high frontal alpha reflects a disengagement of attentional control whereas the transient posterior alpha time-locked to the saccade indicates sensory inhibition of the salient distractor and suppression of bottom-up oculomotor capture. |
Kathryn L. McCabe; Dominique Rich; Carmel M. Loughland; Ulrich Schall; Linda E. Campbell Visual scanpath abnormalities in 22q11.2 deletion syndrome: Is this a face specific deficit? Journal Article In: Psychiatry Research, vol. 189, no. 2, pp. 292–298, 2011. @article{McCabe2011, People with 22q11.2 deletion syndrome (22q11DS) have deficits in face emotion recognition. However, it is not known whether this is a deficit specific to faces, or represents maladaptive information processing strategies to complex stimuli in general. This study examined the specificity of face emotion processing deficits in 22q11DS by exploring recognition accuracy and visual scanpath performance to a Faces task compared to a Weather Scene task. Seventeen adolescents with 22q11DS (11. =females |
Katie L. Meadmore; Itiel E. Dror; Romola S. Bucks; Simon P. Liversedge Eye movements during visuospatial judgements Journal Article In: European Journal of Cognitive Psychology, vol. 23, no. 1, pp. 92–101, 2011. @article{Meadmore2011, The goal of the current research was to determine whether eye movements reflect different underlying cognitive processes associated with visuospatial relation judgements. Ten participants made three different judgements regarding the position of a dot in relation to a bar; an above/below judgement, a near/far judgement, and a precise distance estimation. The results highlight similarities between above/ below and near/far visuospatial judgements; specifically, such binary judgements were fast, reflexive, and did not require precise distance computation. In contrast, estimating distance was comparatively cognitively demanding and required precise distance computation, as evidenced through distinct scan paths. The eye movement data provide significant insight into the cognitive processes underlying visuospatial judgements, showing aspects of visuospatial processing that are similar, as well as those that differ between tasks. |
Muriel T. N. Panouillères; Christian Urquizar; Roméo Salemme; Denis Pélisson In: PLoS ONE, vol. 6, no. 2, pp. e17329, 2011. @article{Panouilleres2011, When goal-directed movements are inaccurate, two responses are generated by the brain: a fast motor correction toward the target and an adaptive motor recalibration developing progressively across subsequent trials. For the saccadic system, there is a clear dissociation between the fast motor correction (corrective saccade production) and the adaptive motor recalibration (primary saccade modification). Error signals used to trigger corrective saccades and to induce adaptation are based on post-saccadic visual feedback. The goal of this study was to determine if similar or different error signals are involved in saccadic adaptation and in corrective saccade generation. Saccadic accuracy was experimentally altered by systematically displacing the visual target during motor execution. Post-saccadic error signals were studied by manipulating visual information in two ways. First, the duration of the displaced target after primary saccade termination was set at 15, 50, 100 or 800 ms in different adaptation sessions. Second, in some sessions, the displaced target was followed by a visual mask that interfered with visual processing. Because they rely on different mechanisms, the adaptation of reactive saccades and the adaptation of voluntary saccades were both evaluated. We found that saccadic adaptation and corrective saccade production were both affected by the manipulations of post-saccadic visual information, but in different ways. This first finding suggests that different types of error signal processing are involved in the induction of these two motor corrections. Interestingly, voluntary saccades required a longer duration of post-saccadic target presentation to reach the same amount of adaptation as reactive saccades. Finally, the visual mask interfered with the production of corrective saccades only during the voluntary saccades adaptation task. These last observations suggest that post-saccadic perception depends on the previously performed action and that the differences between saccade categories of motor correction and adaptation occur at an early level of visual processing. |
Caroline Paquette; Joyce Fung Old age affects gaze and postural coordination Journal Article In: Gait and Posture, vol. 33, no. 2, pp. 227–232, 2011. @article{Paquette2011, Visual tracking of the surrounding environment is an important daily task, often executed simultaneously with the regulation of upright balance. Visual and postural coordination may be affected by aging which is associated with a decline in sensory and motor functions. The aim of the present study was to assess the effects of aging on the control of saccadic and smooth pursuit eye movements when standing on a moving surface. Nineteen young and 12 elderly subjects tracked a visual target presented as unpredictable smooth pursuit or saccadic displacements. Subjects were instructed to maintain gaze on target during quiet stance with or without yaw surface rotations. Elderly subjects followed both saccadic and pursuit targets with less accuracy than young subjects. Moreover, elderly subjects responded with longer time lags during saccadic target shifts and executed more catch-up saccades during smooth pursuits than younger subjects. Standing on a moving surface induced larger target-gaze errors. Catch-up saccades during pursuit occurred more frequently during surface perturbations. Our results suggest that visual tracking abilities decline with age and that postural challenge affects accuracy but not timing of gaze responses. Such declines observed with aging may result from multiple but minor sensory and motor deficits. |
Stacey E. Parrott; Brian R. Levinthal; Steven L. Franconeri Complex attentional control settings Journal Article In: Quarterly Journal of Experimental Psychology, vol. 63, no. 12, pp. 2297–2304, 2011. @article{Parrott2011, The visual system prioritizes information through a variety of mechanisms, including “attentional control settings” that specify features (e.g., colour) that are relevant to current goals. Recent work shows that these control settings may be more complex than previously thought, such that participants can monitor for independent features at different locations (Adamo, Pun, Pratt, & Ferber, 2008). However, this result leaves unclear whether these control settings affect early attentional selection or later target processing. We dissociated between these possibilities in two ways. In Experiment 1, participants were asked to determine whether a target object, which was preceded by an uninformative cue, matched one of two target templates (e.g., a blue vertical object or a green horizontal object). Participants monitored for independent features in the same location, but in different objects, which should reduce the effectiveness of the control setting if it is due to early attentional selection, but not if it is due to later target processing. In Experiment 2, we removed the ability of the cue to prime the target identity, which makes the opposite prediction. Together, the results suggest that complex attentional control settings primarily affect later target identity processing, and not early attentional selection. |
Nikole D. Patson; Tessa Warren Building complex reference objects from dual sets Journal Article In: Journal of Memory and Language, vol. 64, no. 4, pp. 443–459, 2011. @article{Patson2011, There has been considerable psycholinguistic investigation into the conditions that allow separately introduced individuals to be joined into a plural set and represented as a complex reference object (e.g., Eschenbach et al., 1989; Garrod & Sanford, 1982; Koh & Clifton, 2002; Koh et al., 2008; Moxey, Sanford, Sturt, & Morrow, 2004; Sanford & Lockhart, 1990). The current paper reports three eye-tracking experiments that investigate the less-well understood question of what conditions allow pointers to be assigned to the individuals within a previously undifferentiated set, turning it into a complex reference object. The experiments made use of a methodology used in Patson and Ferreira (2009) to distinguish between complex reference objects and undifferentiated sets. Experiments 1 and 2 demonstrated that assigning different properties to the members of an undifferentiated dual set via a conjoined modifier or a comparative modifier transformed it into a complex reference object. Experiment 3 indicated that assigning a property to only one member of an undifferentiated dual set introduced pointers to both members. These results demonstrate that pointers can be established to referents within a plural set without picking them out via anaphors; they set boundaries on the kinds of implicit contrasts between referents that establish pointers; and they illustrate that extremely subtle properties of the semantic and referential context can affect early parsing decisions. |
Alberto Megías; Antonio Maldonado; Andrés Catena; Leandro Luigi Di Stasi; Jesús Serrano; Antonio Cándido Modulation of attention and urgent decisions by affect-laden roadside advertisement in risky driving scenarios Journal Article In: Safety Science, vol. 49, no. 10, pp. 1388–1393, 2011. @article{Megias2011, In road safety literature the effects of emotional content and salience of advertising billboards have been scarcely investigated. The main aim of this work was to uncover how affect-laden roadside advertisements can affect attention - eye-movements - and subsequent risky decisions - braking - on the Honda Riding Trainer motorcycle simulator. Results indicated that the number of fixations and total fixation time elicited by the negative and positive emotional advertisements were larger than the neutral ones. At the same time, negative pictures got later gaze disengagement than positive and neutral ones. This attentional capture results in less eye fixation times on the road relevant region, where the important driving events happen. Finally, the negative emotional valence advertisements sped up braking on subsequent risky situations. Overall results demonstrated how advertisements with emotional content modulate attention allocation and driving decisions in risky situations and might be helpful for designing roadside advertisements regulations and risk prevention programs. |
David Melcher; Manuela Piazza The role of attentional priority and saliency in determining capacity limits in enumeration and visual working memory Journal Article In: PLoS ONE, vol. 6, no. 12, pp. e29296, 2011. @article{Melcher2011, Many common tasks require us to individuate in parallel two or more objects out of a complex scene. Although the mechanisms underlying our abilities to count the number of items, remember the visual properties of objects and to make saccadic eye movements towards targets have been studied separately, each of these tasks require selection of individual objects and shows a capacity limit. Here we show that a common factor–salience–determines the capacity limit in the various tasks. We manipulated bottom-up salience (visual contrast) and top-down salience (task relevance) in enumeration and visual memory tasks. As one item became increasingly salient, the subitizing range was reduced and memory performance for all other less-salient items was decreased. Overall, the pattern of results suggests that our abilities to enumerate and remember small groups of stimuli are grounded in an attentional priority or salience map which represents the location of important items. |
Krista E. Overvliet; E. Azañón; S. Soto-Faraco Somatosensory saccades reveal the timing of tactile spatial remapping Journal Article In: Neuropsychologia, vol. 49, no. 11, pp. 3046–3052, 2011. @article{Overvliet2011, Remapping tactile events from skin to external space is an essential process for human behaviour. It allows us to refer tactile sensations to their actual externally based location, by combining anatomically based somatosensory information with proprioceptive information about the current body posture. We examined the time course of tactile remapping by recording speeded saccadic responses to somatosensory stimuli delivered to the hands. We conducted two experiments in which arm posture varied (crossed or uncrossed), so that anatomical and external frames of reference were either put in spatial conflict or were aligned. The data showed that saccade onset latencies in the crossed hands conditions were slower than in the uncrossed hands condition, suggesting that, in the crossed hands condition, remapping had to be completed before a correct saccade could be executed. Saccades to tactile stimuli when the hands were crossed were sometimes initiated to the wrong direction and then corrected in-flight, resulting in a turn-around saccade. These turn-around saccades were more likely to occur in short-latency responses, compared to onset latencies of saccades that went straight to target. The latter suggests that participants were postponing their saccade until the time the tactile event was represented according to the current body posture. We propose that the difference between saccade onset latencies of crossed and uncrossed hand postures, and between the onset of a turn-around saccade and a straight saccade in the crossed hand posture, reveal the timing of tactile spatial remapping. |
Müge Özbek; Markus Bindemann Exploring the time course of face matching: Temporal constraints impair unfamiliar face identification under temporally unconstrained viewing Journal Article In: Vision Research, vol. 51, no. 19, pp. 2145–2155, 2011. @article{Oezbek2011, The identification of unfamiliar faces has been studied extensively with matching tasks, in which observers decide if pairs of photographs depict the same person (identity matches) or different people (mismatches). In experimental studies in this field, performance is usually self-paced under the assumption that this will encourage best-possible accuracy. Here, we examined the temporal characteristics of this task by limiting display times and tracking observers' eye movements. Observers were required to make match/mismatch decisions to pairs of faces shown for 200, 500, 1000, or 2000. ms, or for an unlimited duration. Peak accuracy was reached within 2000. ms and two fixations to each face. However, intermixing exposure conditions produced a context effect that generally reduced accuracy on identity mismatch trials, even when unlimited viewing of faces was possible. These findings indicate that less than 2. s are required for face matching when exposure times are variable, but temporal constraints should be avoided altogether if accuracy is truly paramount. The implications of these findings are discussed. |
Adam Palanica; Roxane J. Itier Searching for a perceived gaze direction using eye tracking Journal Article In: Journal of Vision, vol. 11, no. 2, pp. 1–13, 2011. @article{Palanica2011, The purpose of the current study was to use eye tracking to better understand the “stare-in-the-crowd effect”—the notion that direct gaze is more easily detected than averted gaze in a crowd of opposite-gaze distractors. Stimuli were displays of four full characters aligned across the monitor (one target and three distractors). Participants completed a visual search task in which they were asked to detect the location of either a direct gaze or an averted gaze target. Reaction time (RT) results indicated faster responses to direct than averted gaze only for characters situated in the far peripheral visual fields. Eye movements confirmed a serial search strategy (definitely ruling out any pop-out effects) and revealed different exploration patterns between hemifields. The latency before the first fixation on target strongly correlated with response RTs. In the LVF, that latency was also faster for direct than averted gaze targets, suggesting that the response asymmetry in favor of direct gaze stemmed from faster direct gaze target detection. In the RVF, however, the response bias to direct gaze seemed not due to a faster visual detection but rather to a different cognitive mechanism. Direct gaze targets were also responded to even faster when their position was congruent with the direction of gaze of distractors. These findings suggest that the detection asymmetry for direct gaze is highly dependent on target position and influenced by social contexts. |
Sebastian Pannasch; Johannes Schulz; Boris M. Velichkovsky On the control of visual fixation durations in free viewing of complex images Journal Article In: Attention, Perception, and Psychophysics, vol. 73, no. 4, pp. 1120–1132, 2011. @article{Pannasch2011, The mechanisms for the substantial variation in the durations of visual fixations in scene perception are not yet well understood. During free viewing of paintings, gaze-contingent irrelevant distractors (Exp. 1) and non-gaze-related time-locked display changes (Exp. 2) were presented. We demonstrated that any visual change-its onset and offset-prolongs the ongoing fixation (i.e., delays the following saccade), strongly suggesting that fixation durations are under the direct control of the stimulus information. The strongest influence of distraction was observed for fixations preceded by saccades within the parafoveal range (<5° of visual angle). We assume that these fixations contribute to the focal in contrast to the ambient mode of attention (Pannasch & Velichkovsky, Visual Cognition, 17, 1109-1131, 2009; Velichkovsky, Memory, 10, 405-419, 2002). Recent findings about two distinct "subpopulations of fixations," one under the direct and another under the indirect control of stimulation (e.g., Henderson & Smith, Visual Cognition, 17, 1055-1082, 2009), are reconsidered in view of these results. |
Manuel Perea; Chie Nakatani; Cees Leeuwen Transposition effects in reading Japanese Kana: Are they orthographic in nature? Journal Article In: Memory & Cognition, vol. 39, no. 4, pp. 700–707, 2011. @article{Perea2011, One critical question for the front end of models of visual-word recognition and reading is whether the stage of letter position coding is purely orthographic or whether phonology is (to some degree) involved. To explore this issue, we conducted a silent reading experiment in Japanese Kana–a script in which orthography and phonology can be easily separated–using a technique that is highly sensitive to phonological effects (i.e., Rayner's (1975) boundary technique). Results showed shorter fixation times on the target word when the parafoveal preview was a transposed-mora nonword (a.ri.me.ka [アリメカ]-a.me.ri.ka [アメリカ]) than when the preview was a replacement-mora nonword (a.ka.ho.ka [アカホカ] -a.me.ri.ka [アメリカ]). More critically, fixation times on the target word were remarkably similar when the parafoveal preview was a transposed-consonant nonword (a.re.mi.ka [アレミカ]-a.ri.me.ka [アリメカ]) and when the parafoveal preview was an orthographic control nonword (a.ke.hi.ka [アケヒカ]-a.me.ri.ka [アメリカ]). Thus, these findings offer strong support for the view that letter/mora position coding during silent reading is orthographic in nature. |
Gerald Pfeffer; Mathias Abegg; A. Talia Vertinsky; Isabella Ceccherini; Francesco Caroli; Jason J. S. Barton The ocular motor features of adult-onset alexander disease: A case and review of the literature Journal Article In: Journal of Neuro-Ophthalmology, vol. 31, no. 2, pp. 155–159, 2011. @article{Pfeffer2011, A 51-year-old Chinese man presented with gaze-evoked nystagmus, impaired smooth pursuit and vestibular ocular reflex cancellation, and saccadic dysmetria, along with a family history suggestive of late-onset autosomal dominant parkinsonism. MRI revealed abnormalities of the medulla and cervical spinal cord typical of adult-onset Alexander disease, and genetic testing showed homozygosity for the p.D295N polymorphic allele in the gene encoding the glial fibrillary acidic protein. A review of the literature shows that ocular signs are frequent in adult-onset Alexander disease, most commonly gaze-evoked nystagmus, pendular nystagmus, and/or oculopalatal myoclonus, and less commonly ptosis, miosis, and saccadic dysmetria. These signs are consistent with the propensity of adult-onset Alexander disease to cause medullary abnormalities on neuroimaging. |
Tobias Pflugshaupt; Julia Suchan; Marc André Mandler; Alexander N. Sokolov; Susanne Trauzettel-Klosinski; Hans-Otto Karnath Do patients with pure alexia suffer from a specific word form processing deficit? Evidence from 'wrods with trasnpsoed letetrs' Journal Article In: Neuropsychologia, vol. 49, no. 5, pp. 1294–1301, 2011. @article{Pflugshaupt2011, It is widely accepted that letter-by-letter reading and a pronounced increase in reading time as a function of word length are the hallmark features of pure alexia. Why patients show these two phenomena with respect to underlying cognitive mechanisms is, however, much less clear. Two main hypotheses have been proposed, i.e. impaired discrimination of letters and deficient processing of word forms. While the former deficit can easily be investigated in isolation, previous findings favouring the latter seem confounded. Applying a word reading paradigm with systematically manipulated letter orders in two patients with pure alexia, we demonstrate a word form processing deficit that is not attributable to sublexical letter discrimination difficulties. Moreover, pure alexia-like fixation patterns could be induced in healthy adults by having them read sentences including words with transposed letters, so-called 'jumbled words'. This further corroborates a key role of deficient word form processing in pure alexia. With regard to basic reading research, the present study extends recent evidence for relative, rather than precise, encoding of letter position in the brain.. |
Anna Oleksiak; P. Christiaan Klink; Albert Postma; Ineke J. M. Ham; Martin J. Lankheet; Richard J. A. Wezel Spatial summation in macaque parietal area 7a follows a winner-take-all rule Journal Article In: Journal of Neurophysiology, vol. 105, no. 3, pp. 1150–1158, 2011. @article{Oleksiak2011, While neurons in posterior parietal cortex have been found to signal the presence of a salient stimulus among multiple items in a display, spatial summation within their receptive field in the absence of an attentional bias has never been investigated. This information, however, is indispensable when one investigates the mechanisms of spatial attention and competition between multiple visual objects. To examine the spatial summation rule in parietal area 7a neurons, we trained rhesus monkeys to fixate on a central cross while two identical stimuli were briefly displayed in a neuron's receptive field. The response to a pair of dots was compared with the responses to the same dots when they were presented individually. The scaling and power parameters of a generalized summation algorithm varied greatly, both across neurons and across combinations of stimulus locations. However, the averaged response of the recorded population of 7a neurons was consistent with a winner-take-all rule for spatial summation. A control experiment where a monkey covertly attended to both stimuli simultaneously suggests that attention introduces additional competition by facilitating the less optimal stimulus. Thus an averaging stage is introduced between ∼ 200 and 300 ms of the response to a pair of stimuli. In short, the summation algorithm over the population of area 7a neurons carries the signature of a winner-take-all operation, with spatial attention possibly influencing the temporal dynamics of stimulus competition, that is the moment that the "winner" takes "victory" over the "loser" stimulus. |
Bettina Olk; Yu Jin Effects of aging on switching the response direction of pro-and antisaccades Journal Article In: Experimental Brain Research, vol. 208, no. 1, pp. 139–150, 2011. @article{Olk2011, The present study investigated effects of task switching between pro- and antisaccades and switching the direction of these saccades (response switching) on performance of younger and older adults. Participants performed single-task blocks, in which only pro- or only antisaccades had to be made as well as mixed-task blocks, in which pro- and antisaccades were required. Analysis of specific task switch effects in the mixed-task blocks showed switch costs for error rates for prosaccades for both groups, suggesting that antisaccade task rules persisted and affected the following prosaccade. The comparison between single- and mixed-task blocks showed that mixing costs were either equal or smaller for older than younger participants, indicating that the older participants were well able to keep task sets in working memory. The most prominent age difference that was observed for response switching was that for the older but not younger group task switching and response switching interacted, resulting in less errors when two consecutive antisaccades were made in the same direction. This finding is best explained with a facilitation of these consecutive antisaccades. The present study clearly demonstrated the impact of response switching and a difference between age groups, underlining the importance of considering this factor when investigating pro- and antisaccades, especially antisaccades, and when investigating task switching and aging. |
Samantha C. Otero; Brendan S. Weekes; Samuel B. Hutton Pupil size changes during recognition memory Journal Article In: Psychophysiology, vol. 48, no. 10, pp. 1346–1353, 2011. @article{Otero2011, Pupils dilate to a greater extent when participants view old compared to new items during recognition memory tests. We report three experiments investigating the cognitive processes associated with this pupil old/new effect. Using a remember/know procedure, we found that the effect occurred for old items that were both remembered and known at recognition, although it was attenuated for known compared to remembered items. In Experiment 2, the pupil old/new effect was observed when items were presented acoustically, suggesting the effect does not depend on low-level visual processes. The pupil old/new effect was also greater for items encoded under deep compared to shallow orienting instructions, suggesting it may reflect the strength of the underlying memory trace. Finally, the pupil old/new effect was also found when participants falsely recognized items as being old. We propose that pupils respond to a strength-of-memory signal and suggest that pupillometry provides a useful technique for exploring the underlying mechanisms of recognition memory. |
Jorge Otero-Millan; Stephen L. Macknik; Apollo Robbins; Susana Martinez-Conde Stronger misdirection in curved than in straight motion Journal Article In: Frontiers in Human Neuroscience, vol. 5, pp. 133, 2011. @article{OteroMillan2011, Illusions developed by magicians are a rich and largely untapped source of insight into perception and cognition. Here we show that curved motion, as employed by the magician in a classic sleight of hand trick, generates stronger misdirection than rectilinear motion, and that this difference can be explained by the differential engagement of the smooth pursuit and the saccadic oculomotor systems. This research exemplifies how the magician's intuitive understanding of the spectator's mindset can surpass that of the cognitive scientist in specific instances, and that observation-based behavioral insights developed by magicians are worthy of quantitative investigation in the neuroscience laboratory. |
Jorge Otero-Millan; Alessandro Serra; R. John Leigh; Xoana G. Troncoso; Stephen L. Macknik; Susana Martinez-Conde Distinctive features of saccadic intrusions and microsaccades in progressive supranuclear palsy Journal Article In: Journal of Neuroscience, vol. 31, no. 12, pp. 4379–4387, 2011. @article{OteroMillan2011a, The eyes do not stay perfectly still during attempted fixation; fixational eye movements and saccadic intrusions (SIs) continuously change the position of gaze. The most common type of SI, square-wave jerks (SWJs), consists of saccade pairs that appear purely horizontal on clinical inspection: the first saccade moves the eye away from the fixation target, and after a short interval, the second saccade brings it back toward the target. SWJs are prevalent in certain neurological disorders, including progressive supranuclear palsy (PSP). Here, we developed an objective method to identify SWJs. We found that SWJs are more frequent, larger, and more markedly horizontal in PSP patients than in healthy human subjects. Furthermore, the loss of a vertical component in fixational saccades and SWJs was the eye movement feature that best distinguished PSP patients from controls. We moreover determined that, in PSP patients and controls, the larger the saccade the more likely it was part of a SWJ. Furthermore, saccades produced by PSP patients had equivalent properties whether they were part of a SWJ or not, suggesting that normal fixational saccades (microsaccades) are rare in PSP. We propose that fixational saccades and SIs are generated by the same neural circuit and that, both in PSP patients and in controls, SWJs result from a coupling mechanism that generates a second corrective saccade shortly after a large fixation saccade. Because of brainstem and/or cerebellum impairment, fixational saccades in PSP are abnormally large and thus more likely to trigger a corrective saccade, giving rise to SWJs. |
Mathias Abegg; Dara S. Manoach; Jason J. S. Barton Knowing the future: Partial foreknowledge effects on the programming of prosaccades and antisaccades Journal Article In: Vision Research, vol. 51, no. 1, pp. 215–221, 2011. @article{Abegg2011, Foreknowledge about the demands of an upcoming trial may be exploited to optimize behavioural responses. In the current study we systematically investigated the benefits of partial foreknowledge - that is, when some but not all aspects of a future trial are known in advance. For this we used an ocular motor paradigm with horizontal prosaccades and antisaccades. Predictable sequences were used to create three partial foreknowledge conditions: one with foreknowledge about the stimulus location only, one with foreknowledge about the task set only, and one with foreknowledge about the direction of the required response only. These were contrasted with a condition of no-foreknowledge and a condition of complete foreknowledge about all three parameters. The results showed that the three types of foreknowledge affected saccadic efficiency differently. While foreknowledge about stimulus-location had no effect on efficiency, task foreknowledge had some effect and response-foreknowledge was as effective as complete foreknowledge. Foreknowledge effects on switch costs followed a similar pattern in general, but were not specific for switching of the trial attribute for which foreknowledge was available. We conclude that partial foreknowledge has a differential effect on efficiency, most consistent with preparatory activation of a motor schema in advance of the stimulus, with consequent benefits for both switched and repeated trials. |
Parag K. Mital; Tim J. Smith; Robin L. Hill; John M. Henderson Clustering of gaze during dynamic scene viewing is predicted by motion Journal Article In: Cognitive Computation, vol. 3, no. 1, pp. 5–24, 2011. @article{Mital2011, Where does one attend when viewing dynamic scenes? Research into the factors influencing gaze location during static scene viewing have reported that low-level visual features contribute very little to gaze location especially when opposed by high-level factors such as viewing task. However, the inclusion of transient features such as motion in dynamic scenes may result in a greater influence of visual features on gaze allocation and coordination of gaze across viewers. In the present study, we investigated the contribution of low-to mid-level visual features to gaze location during free-viewing of a large dataset of videos ranging in content and length. Signal detection analysis on visual features and Gaussian Mixture Models for clustering gaze was used to identify the contribution of visual features to gaze location. The results show that mid-level visual features including corners and orientations can distinguish between actual gaze locations and a randomly sampled baseline. However, temporal features such as flicker, motion, and their respective contrasts were the most predictive of gaze location. Additionally, moments in which all viewers' gaze tightly clustered in the same location could be predicted by motion. Motion and mid-level visual features may influence gaze allocation in dynamic scenes, but it is currently unclear whether this influence is involuntary or due to correlations with higher order factors such as scene semantics. |
Holger Mitterer The mental lexicon is fully specified: Evidence from eye-tracking Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 37, no. 2, pp. 496–513, 2011. @article{Mitterer2011, Four visual-world experiments, in which listeners heard spoken words and saw printed words, compared an optimal-perception account with the theory of phonological underspecification. This theory argues that default phonological features are not specified in the mental lexicon, leading to asymmetric lexical matching: Mismatching input (pin) activates lexical entries with underspecified coronal stops (tin), but lexical entries with specified labial stops (pin) are not activated by mismatching input (tin). The eye-tracking data failed to show such a pattern. Although words that were phonologically similar to the spoken target attracted more looks than did unrelated distractors, this effect was symmetric in Experiment 1 with minimal pairs (tin-pin) and in Experiments 2 and 3 with words with an onset overlap (peacock-teacake). Experiment 4 revealed that /t/-initial words were looked at more frequently if the spoken input mismatched only in terms of place than if it mismatched in place and voice, contrary to the assumption that /t/ is unspecified for place and voice. These results show that speech perception uses signal-driven information to the fullest, as was predicted by an optimal perception account. |
Korbinian Moeller; Elise Klein; Hans-Christoph Nuerk Three processes underlying the carry effect in addition - Evidence from eye tracking Journal Article In: British Journal of Psychology, vol. 102, no. 3, pp. 623–645, 2011. @article{Moeller2011, Recent research indicated that processes of unit-decade integration pose particular difficulty on multi-digit addition. In fact, longer response latencies as well as higher error rates have been observed for addition problems involving a carry operation (e.g., 18 +27) compared to problems not requiring a carry (e.g., 13 +32). However, the cognitive instantiation of this carry effect remained unknown. In the current study, this question was pursued by recording participants' eye fixation behaviour during addition problem verification. Analyses of the eye fixation data suggested a prominent role of the unit digits of the summands. The need for a carry seems to be recognized very early during the encoding of the problem after initial unit sum calculation has established the basis for the no carry/carry detection. Additionally, processes related to the actual carry execution seemed to be associated with the processing of the decade digit of the solution probe but were less unambiguous. Taken together, our findings indicate that unit-based calculations and the associated recognition that a carry is needed as well as its completion determine the difficulty of carry addition problems. On a more general level, this study shows how the nature of numerical-cognitive processes can be further differentiated by the evaluation of eye movement measures. |
Korbinian Moeller; Elise Klein; Hans-Christoph Nuerk (No) small adults: Children's processing of carry addition problems Journal Article In: Developmental Neuropsychology, vol. 36, no. 6, pp. 702–720, 2011. @article{Moeller2011a, Analyses of eye-fixation data in adults suggested that the carry effect in addition is determined by the unit digits of the summands. Correspondingly, we recorded children's eye fixation behavior in a choice reaction paradigm. As for adults the carry effect was most pronounced on the unit digits of the summands. However, children's fixation pattern differed reliably from that of adults in other important aspects. While these data suggested common processes in children and adults for performing a carry in mental addition, children's eye fixation data indicated a less flexible processing style primarily based on calculating the correct result. |
Sarim Mohammad; Irene Gottlob; Anil Kumar; Mervyn G. Thomas; Christopher Degg; Viral Sheth; Frank A. Proudlock The functional significance of foveal abnormalities in albinism measured using spectral-domain optical coherence tomography Journal Article In: Ophthalmology, vol. 118, no. 8, pp. 1645–1652, 2011. @article{Mohammad2011, Purpose: The relationship between foveal abnormalities in albinism and best-corrected visual acuity (BCVA) is unclear. High-resolution spectral-domain optical coherence tomography (SD OCT) was used to quantify foveal retinal layer thicknesses and to assess the functional significance of foveal morphologic features in patients with albinism. Design: Cross-sectional study. Participants: Forty-seven patients with albinism and 20 healthy control volunteers were recruited to the study. Methods: Using high-resolution SD OCT, 7×7×2-mm volumetric scans of the fovea were acquired (3-μm axial resolution). The B scan nearest the center of the fovea was identified using signs of foveal development. The thickness of each retinal layer at the fovea and foveal pit depth were quantified manually using ImageJ software and were compared with BCVA. Main Outcome Measures: Total retinal thickness, foveal pit depth, photoreceptor layer thickness, and processing layer thickness in relation to BCVA. Results: Total photoreceptor layer thickness at the fovea was correlated highly to BCVA (P = 0.0008; r = 0.501). Of the photoreceptor layers, the outer segment length was correlated most strongly to BCVA (P<0.0001; r = 0.641). In contrast, there was no significant correlation between either total retinal thickness or pit depth and BCVA (P>0.05). This was because of an inverse correlation between total photoreceptor layer thickness and total processing layer thickness (P<0.0001; r = 0.696). Conclusions: Neither the total retinal thickness nor the pit depth are reliable indicators of visual deficit, because patients with similar overall retinal thickness had widely varying foveal morphologic features. In albinism, the size of the photoreceptor outer segment was found to be the strongest predictor of BCVA. These results suggest that detailed SD OCT images of photoreceptor anatomic features provide a useful tool in assessing the visual potential in patients with albinism. |
Jeff Moher; Jared Abrams; Howard E. Egeth; Steven Yantis; Veit Stuphorn Trial-by-trial adjustments of top-down set modulate oculomotor capture Journal Article In: Psychonomic Bulletin & Review, vol. 18, no. 5, pp. 897–903, 2011. @article{Moher2011, The role of top-down control in visual search has been a subject of much debate. Recent research has focused on whether attentional and oculomotor capture by irrelevant salient distractors can be modulated through top-down control, and if so, whether top-down control can be rapidly initiated based on current task goals. In the present study, participants searched for a unique shape in an array containing otherwise homogeneous shapes. A cue prior to each trial indicated the probability that an irrelevant color singleton distractor would appear on that trial. Initial saccades were less likely to land on the target and participants took longer to initiate a saccade to the target when a color distractor was present than when it was absent; this cost was greatly reduced on trials in which the probability that a distractor would appear was high, as compared to when the probability was low. These results suggest that top-down control can modulate oculomotor capture in visual search, even in a singleton search task in which distractors are known to readily capture both attention and the eyes. Furthermore, the results show that top-down distractor suppression mechanisms can be initiated quickly in anticipation of irrelevant salient distractors and can be adjusted on a trial-by-trial basis. |
Pierre Morel; Sophie Deneve; Pierre Baraduc Optimal and suboptimal use of postsaccadic vision in sequences of saccades Journal Article In: Journal of Neuroscience, vol. 31, no. 27, pp. 10039–10049, 2011. @article{Morel2011, Saccades are imprecise, due to sensory and motor noise. To avoid an accumulation of errors during sequences of saccades, a prediction derived from the efference copy can be combined with the reafferent visual feedback to adjust the following eye movement. By varying the information quantity of the visual feedback, we investigated how the reliability of the visual information affects the postsaccadic update in humans. Two elements of the visual scene were manipulated, the saccade target or the background, presented either together or in isolation. We determined the weight of the postsaccadic visual information by measuring the effect of intrasaccadic visual shifts on the following saccade. We confirmed that the weight of visual information evolves with information quantity as predicted for a statistically optimal system. In particular, we found that the visual background alone can guide the postsaccadic update, and that information from target and background are optimally combined. Moreover, these visual weights are adjusted dynamically and on a trial-to-trial basis to the level of visual noise determined by target eccentricity and reaction time. In contrast, we uncovered a dissociation between the visual signals used to update the next planned saccade (main saccade) and those used to generate an involuntary corrective saccade. The latter was exclusively based on visual information about the target, and discarded all information about the background: a suboptimal use of visual evidence. |
Sofie Moresi; Jos J. Adam; Jons Rijcken; Harm Kuipers; Marianne Severens; Pascal W. M. Van Gerven Response preparation with adjacent versus overlapped hands: A pupillometric study Journal Article In: International Journal of Psychophysiology, vol. 79, no. 2, pp. 280–286, 2011. @article{Moresi2011, Preparatory cues facilitate performance in speeded choice tasks. It is debated, however, whether the lateralized neuro-anatomical organization of the human motor system contributes to this facilitation. To investigate this issue, we examined response preparation in a finger-cuing task using two conditions. In the hands adjacent condition, the hands were placed adjacently to each other with index and middle fingers placed on four linearly arrayed response keys. In the overlapped hand placement condition, the fingers of different hands alternated, thus dissociating hand and spatial position factors. Preparatory cues specified a subset of two fingers. Left-right cues specified the two leftmost or two rightmost fingers. Inner-outer cues specified the two inner or outer fingers. Alternate cues specified the first and third, or the second and fourth finger in the response set. In addition to reaction time and response errors, we measured the pupillary response to assess the cognitive processing load associated with response preparation. Results showed stronger pupil dilations (and also longer RTs and more errors) for the overlapped than for the adjacent hand placement condition, reflecting an overall increase in cognitive processing load. Furthermore, the negative impact of overlapping the hands on pupil dilation interacted with cue type, indicating that left-right cues (associated with two fingers on one hand) suffered most from overlapping the hands. With the hands overlapped, alternate cues (now associated with two fingers on the same hand) produced the shortest RTs. These findings demonstrate the importance of motoric factors in response preparation. |
Isamu Motoyoshi Attentional modulation of temporal contrast sensitivity in human vision Journal Article In: PLoS ONE, vol. 6, no. 4, pp. e19303, 2011. @article{Motoyoshi2011, Recent psychophysical studies have shown that attention can alter contrast sensitivities for temporally broadband stimuli such as flashed gratings. The present study examined the effect of attention on the contrast sensitivity for temporally narrowband stimuli with various temporal frequencies. Observers were asked to detect a drifting grating of 0-40 Hz presented gradually in the peripheral visual field with or without a concurrent letter identification task in the fovea. We found that removal of attention by the concurrent task reduced the contrast sensitivity for gratings with low temporal frequencies much more profoundly than for gratings with high temporal frequencies and for flashed gratings. The analysis revealed that the temporal contrast sensitivity function had a more band-pass shape with poor attention. Additional experiments showed that this was also true when the target was presented in various levels of luminance noise. These results suggest that regardless of the presence of external noise, attention extensively modulates visual sensitivity for sustained retinal inputs. |
Christina Moutsiana; David T. Field; John P. Harris The neural basis of centre-surround interactions in visual motion processing Journal Article In: PLoS ONE, vol. 6, no. 7, pp. e22902, 2011. @article{Moutsiana2011, Perception of a moving visual stimulus can be suppressed or enhanced by surrounding context in adjacent parts of the visual field. We studied the neural processes underlying such contextual modulation with fMRI. We selected motion selective regions of interest (ROI) in the occipital and parietal lobes with sufficiently well defined topography to preclude direct activation by the surround. BOLD signal in the ROIs was suppressed when surround motion direction matched central stimulus direction, and increased when it was opposite. With the exception of hMT+/V5, inserting a gap between the stimulus and the surround abolished surround modulation. This dissociation between hMT+/V5 and other motion selective regions prompted us to ask whether motion perception is closely linked to processing in hMT+/V5, or reflects the net activity across all motion selective cortex. The motion aftereffect (MAE) provided a measure of motion perception, and the same stimulus configurations that were used in the fMRI experiments served as adapters. Using a linear model, we found that the MAE was predicted more accurately by the BOLD signal in hMT+/V5 than it was by the BOLD signal in other motion selective regions. However, a substantial improvement in prediction accuracy could be achieved by using the net activity across all motion selective cortex as a predictor, suggesting the overall conclusion that visual motion perception depends upon the integration of activity across different areas of visual cortex. |
Neil G. Muggleton; Roger Kalla; Chi-Hung Juan; Vincent Walsh Dissociating the contributions of human frontal eye fields and posterior parietal cortex to visual search Journal Article In: Journal of Neurophysiology, vol. 105, no. 6, pp. 2891–2896, 2011. @article{Muggleton2011, Imaging, lesion, and transcranial magnetic stimulation (TMS) studies have implicated a number of regions of the brain in searching for a target defined by a combination of attributes. The necessity of both frontal eye fields (FEF) and posterior parietal cortex (PPC) in task performance has been shown by the application of TMS over these regions. The effects of stimulation over these two areas have, thus far, proved to be remarkably similar and the only dissociation reported being in the timing of their involvement. We tested the hypotheses that 1) FEF contributes to performance in terms of visual target detection (possibly by modulation of activity in extrastriate areas with respect to the target), and 2) PPC is involved in translation of visual information for action. We used a task where the presence (and location) of the target was indicated by an eye movement. Task disruption was seen with FEF TMS (with reduced accuracy on the task) but not with PPC stimulation. When a search task requiring a manual response was presented, disruption with PPC TMS was seen. These results show dissociation of FEF and PPC contributions to visual search performance and that PPC involvement seems to be dependent on the response required by the task, whereas this is not the case for FEF. This supports the idea of FEF involvement in visual processes in a manner that might not depend on the required response, whereas PPC seems to be involved when a manual motor response to a stimulus is required. |
Marcus R. Munafò; Nicole Roberts; Linda Bauld; Ute Leaonards Plain packaging increases visual attention to health warnings on cigarette packs in non-smokers and weekly smokers but not daily smokers Journal Article In: Addiction, vol. 106, pp. 1505–1510, 2011. @article{Munafo2011, AIMS: To assess the impact of plain packaging on visual attention towards health warning information on cigarette packs. DESIGN: Mixed-model experimental design, comprising smoking status as a between-subjects factor, and package type (branded versus plain) as a within-subjects factor. SETTING: University laboratory. PARTICIPANTS: Convenience sample of young adults, comprising non-smokers (n = 15), weekly smokers (n = 14) and daily smokers (n = 14). MEASUREMENTS: Number of saccades (eye movements) towards health warnings on cigarette packs, to directly index visual attention. FINDINGS: Analysis of variance indicated more eye movements (i.e. greater visual attention) towards health warnings compared to brand information on plain packs versus branded packs. This effect was observed among non-smokers and weekly smokers, but not daily smokers. CONCLUSION: Among non-smokers and non-daily cigarette smokers, plain packaging appears to increase visual attention towards health warning information and away from brand information. |
Marnix Naber; Stefan Frässle; Wolfgang Einhäuser Perceptual rivalry: Reflexes reveal the gradual nature of visual awareness Journal Article In: PLoS ONE, vol. 6, no. 6, pp. e20910, 2011. @article{Naber2011, Rivalry is a common tool to probe visual awareness: a constant physical stimulus evokes multiple, distinct perceptual interpretations (‘‘percepts'') that alternate over time. Percepts are typically described as mutually exclusive, suggesting that a discrete (all-or-none) process underlies changes in visual awareness. Here we follow two strategies to address whether rivalry is an all-or-none process: first, we introduce two reflexes as objective measures of rivalry, pupil dilation and optokinetic nystagmus (OKN); second, we use a continuous input device (analog joystick) to allow observers a gradual subjective report. We find that the ‘‘reflexes'' reflect the percept rather than the physical stimulus. Both reflexes show a gradual dependence on the time relative to perceptual transitions. Similarly, observers' joystick deflections, which are highly correlated with the reflex measures, indicate gradual transitions. Physically simulating wave-like transitions between percepts suggest piece-meal rivalry (i.e., different regions of space belonging to distinct percepts) as one possible explanation for the gradual transitions. Furthermore, the reflexes show that dominance durations depend on whether or not the percept is actively reported. In addition, reflexes respond to transitions with shorter latencies than the subjective report and show an abundance of short dominance durations. This failure to report fast changes in dominance may result from limited access of introspection to rivalry dynamics. In sum, reflexes reveal that rivalry is a gradual process, rivalry's dynamics is modulated by the required action (response mode), and that rapid transitions in perceptual dominance can slip away from awareness. |
Andrey R. Nikolaev; Chie Nakatani; Gijs Plomp; Peter Jurica; Cees Leeuwen Eye fixation-related potentials in free viewing identify encoding failures in change detection Journal Article In: NeuroImage, vol. 56, no. 3, pp. 1598–1607, 2011. @article{Nikolaev2011, We considered the hypothesis that spontaneous dissociation between the direction of attention and eye movement causes encoding failure in change detection. We tested this hypothesis by analyzing eye fixation-related potentials (EFRP) at the encoding stage of a change blindness task; when participants freely inspect a scene containing an unmarked target region, in which a change will occur in a subsequent presentation. We measured EFRP amplitude prior to the execution of a saccade, depending on its starting or landing position relative to the target region. For those landings inside the target region, we found a difference in EFRP between correct detection and failure. Overall, correspondence between EFRP amplitude and the size of the saccade predicted successful detection of change; lack of correspondence was followed by change blindness. By contrast, saccade sizes and fixation durations around the target region were unrelated to subsequent change detection. Since correspondence between EFRP and eye movement indicates that overt attention was given to the target region, we concluded that overt attention is needed for successful encoding and that dissociation between eye movement and attention leads to change blindness. |
Shinji Nishimoto; Jack L. Gallant A three-dimensional spatiotemporal receptive field model explains responses of area MT neurons to naturalistic movies Journal Article In: Journal of Neuroscience, vol. 31, no. 41, pp. 14551–14564, 2011. @article{Nishimoto2011, Area MT has been an important target for studies of motion processing. However, previous neurophysiological studies of MT have used simple stimuli that do not contain many of the motion signals that occur during natural vision. In this study we sought to determine whether views of area MT neurons developed using simple stimuli can account for MT responses under more naturalistic conditions. We recorded responses from macaque area MT neurons during stimulation with naturalistic movies. We then used a quantitative modeling framework to discover which specific mechanisms best predict neuronal responses under these challenging conditions. We find that the simplest model that accurately predicts responses of MT neurons consists of a bank of V1-like filters, each followed by a compressive nonlinearity, a divisive nonlinearity, and linear pooling. Inspection of the fit models shows that the excitatory receptive fields of MT neurons tend to lie on a single plane within the three-dimensional spatiotemporal frequency domain, and suppressive receptive fields lie off this plane. However, most excitatory receptive fields form a partial ring in the plane and avoid low temporal frequencies. This receptive field organization ensures that most MT neurons are tuned for velocity but do not tend to respond to ambiguous static textures that are aligned with the direction of motion. In sum, MT responses to naturalistic movies are largely consistent with predictions based on simple stimuli. However, models fit using naturalistic stimuli reveal several novel properties of MT receptive fields that had not been shown in prior experiments. |
Yasuki Noguchi; Shinsuke Shimojo; Ryusuke Kakigi; Minoru Hoshiyama An integration of color and motion information in visual scene analyses Journal Article In: Psychological Science, vol. 22, no. 2, pp. 153–158, 2011. @article{Noguchi2011, To analyze complex scenes efficiently, the human visual system performs perceptual groupings based on various features (e.g., color and motion) of the visual elements in a scene. Although previous studies demonstrated that such groupings can be based on a single feature (e.g., either color or motion information), here we show that the visual system also performs scene analyses based on a combination of two features. We presented subjects with a mixture of red and green dots moving in various directions. Although the pairings between color and motion information were variable across the dots (e.g., one red dot moved upward while another moved rightward), subjects' perceptions of the color-motion pairings were significantly biased when the randomly paired dots were flanked by additional dots with consistent color-motion pairings. These results indicate that the visual system resolves local ambiguities in color-motion pairings using unambiguous pairings in surrounds, demonstrating a new type of scene analysis based on the combination of two featural cues. |
Lauri Nummenmaa; Jari K. Hietanen; Manuel G. Calvo; Jukka Hyönä Food catches the eye but not for everyone: A BMI-contingent attentional bias in rapid detection of nutriments Journal Article In: PLoS ONE, vol. 6, no. 5, pp. e19215, 2011. @article{Nummenmaa2011, An organism's survival depends crucially on its ability to detect and acquire nutriment. Attention circuits interact with cognitive and motivational systems to facilitate detection of salient sensory events in the environment. Here we show that the human attentional system is tuned to detect food targets among nonfood items. In two visual search experiments participants searched for discrepant food targets embedded in an array of nonfood distracters or vice versa. Detection times were faster when targets were food rather than nonfood items, and the detection advantage for food items showed a significant negative correlation with Body Mass Index (BMI). Also, eye tracking during searching within arrays of visually homogenous food and nonfood targets demonstrated that the BMI-contingent attentional bias was due to rapid capturing of the eyes by food items in individuals with low BMI. However, BMI was not associated with decision times after the discrepant food item was fixated. The results suggest that visual attention is biased towards foods, and that individual differences in energy consumption–as indexed by BMI–are associated with differential attentional effects related to foods. We speculate that such differences may constitute an important risk factor for gaining weight. |
Olufunmilola Ogun; Jayalakshmi Viswanathan; Jason J. S. Barton The effect of central (macula) sparing of contralateral line bisection bias: A study with virtual hemianopia Journal Article In: Neuropsychologia, vol. 49, no. 12, pp. 3377–3382, 2011. @article{Ogun2011, Hemianopic patients show a contralesional bisection bias, but it is unclear whether this is a consequence of their field loss or related to extrastriate damage. One observation cited against the former is that hemianopic bisection bias does not vary with the degree of central (macular) sparing; however, it is unclear to what extent central sparing should affect this bias. Our goal was to determine the effect of central sparing on line bisection biases from field loss alone, with two approaches. First, we studied 12 healthy subjects viewing lines under conditions of virtual hemianopia, created by a gaze-contingent technique. Second, we calculated the effect predicted by a visuospatial model of the effect of central magnification on line representations in the visual system. Our results first replicated the contralateral line bisection bias with hemianopia, confirming that this can be generated by visual hemifield loss in the absence of extrastriate damage. Central sparing had only a modest effect on hemianopic bisection bias, with only slightly less bias with 10° compared to 2° of central sparing. In accordance with these empiric data, computing the center of mass for line representations in our model showed only a shallow decline in bisection bias as central sparing increased from 0 to 10°. We conclude that contralateral bisection bias only decreases slightly with central sparing, and that the absence of a statistically significant effect of central sparing in patients cannot be taken as evidence against a visual origin of contralateral hemianopic line bisection bias. |
Sven Ohl; Stephan A. Brandt; Reinhold Kliegl Secondary (micro-)saccades: The influence of primary saccade end point and target eccentricity on the process of postsaccadic fixation Journal Article In: Vision Research, vol. 51, no. 23-24, pp. 2340–2347, 2011. @article{Ohl2011, We examine how the size of saccadic under-/overshoot and target eccentricity influence the latency, amplitude and orientation of secondary (micro-)saccades. In our experiment, a target appeared at an eccentricity of either 6° or 14° of visual angle. Subjects were instructed to direct their gaze as quickly as possible to the target and hold fixation at the new location until the end of the trial. Typically, increasing saccadic error is associated with faster and larger secondary saccades. We show that secondary saccades at distant in contrast to close targets have in a specific error range a shorter latency, larger amplitude, and follow more often the direction of the primary saccade. Finally, we demonstrate that an undershooting primary saccade is followed almost exclusively by secondary saccades into the same direction while overshooting primary saccades are followed by secondary saccades into both directions. This supports the notion that under- and overshooting imply different consequences for postsaccadic oculomotor processing. Results are discussed using a model, introduced by Rolfs, Kliegl, and Engbert (2008), to account for the generation of microsaccades. We argue that the dynamic interplay of target eccentricity and the magnitude of the saccadic under-/overshoot can be explained by a different strength of activation in the two hemispheres of the saccadic motor map in this model. |
Sébastien Miellet; Roberto Caldara; Philippe G. Schyns Local jekyll and global hyde: The dual identity of face identification Journal Article In: Psychological Science, vol. 22, no. 12, pp. 1518–1526, 2011. @article{Miellet2011, The main concern in face-processing research is to understand the processes underlying the identification of faces. In the study reported here, we addressed this issue by examining whether local or global information supports face identification. We developed a new methodology called "iHybrid." This technique combines two famous identities in a gaze-contingent paradigm, which simultaneously provides local, foveated information from one face and global, complementary information from a second face. Behavioral face-identification performance and eye-tracking data showed that the visual system identified faces on the basis of either local or global information depending on the location of the observer's first fixation. In some cases, a given observer even identified the same face using local information on one trial and global information on another trial. A validation in natural viewing conditions confirmed our findings. These results clearly demonstrate that face identification is not rooted in a single, or even preferred, information-gathering strategy. |
Mark Mills; Andrew Hollingworth; Stefan Van der Stigchel; Lesa Hoffman; Michael D. Dodd Examining the influence of task set on eye movements and fixations Journal Article In: Journal of Vision, vol. 11, no. 8, pp. 1–15, 2011. @article{Mills2011, The purpose of the present study was to examine the influence of task set on the spatial and temporal characteristics of eye movements during scene perception. In previous work, when strong control was exerted over the viewing task via specification of a target object (as in visual search), task set biased spatial, rather than temporal, parameters of eye movements. Here, we find that more participant-directed tasks (in which the task establishes general goals of viewing rather than specific objects to fixate) affect not only spatial (e.g., saccade amplitude) but also temporal parameters (e.g., fixation duration). Further, task set influenced the rate of change in fixation duration over the course of viewing but not saccade amplitude, suggesting independent mechanisms for control of these parameters. |
Milica Milosavljevic; Christof Koch; Antonio Rangel Consumers can make decisions in as little as a third of a second Journal Article In: Judgment and Decision Making, vol. 6, no. 6, pp. 520–530, 2011. @article{Milosavljevic2011, We make hundreds of decisions every day, many of them extremely quickly and without much explicit deliberation. This motivates two important open questions: What is the minimum time required to make choices with above chance accuracy? What is the impact of additional decision-making time on choice accuracy? We investigated these questions in four experiments in which subjects made binary food choices using saccadic or manual responses, under either “speed” or “accuracy” instructions. Subjects were able to make above chance decisions in as little as 313 ms, and choose their preferred food item in over 70% of trials at average speeds of 404 ms. Further, slowing down their responses by either asking them explicitly to be confident about their choices, or to respond with hand movements, generated about a 10% increase in accuracy. Together, these results suggest that consumers can make accurate every-day choices, akin to those made in a grocery store, at significantly faster speeds than previously reported. |
Milica Milosavljevic; Eric Madsen; Christof Koch; Antonio Rangel Fast saccades toward numbers: Simple number comparisons can be made in as little as 230 ms Journal Article In: Journal of Vision, vol. 11, no. 4, pp. 1–12, 2011. @article{Milosavljevic2011a, Visual psychophysicists have recently developed tools to measure the maximal speed at which the brain can accurately carry out different types of computations (H. Kirchner & S. J. Thorpe, 2006). We use this methodology to measure the maximal speed with which individuals can make magnitude comparisons between two single-digit numbers. We find that individuals make such comparisons with high accuracy in 306 ms on average and are able to perform above chance in as little as 230 ms. We also find that maximal speeds are similar for "larger than" and "smaller than" number comparisons and in a control task that simply requires subjects to identify the number in a number-letter pair. The results suggest that the brain contains dedicated processes involved in implementing basic number comparisons that can be deployed in parallel with processes involved in low-level visual processing. |
David M. Milstein; Michael C. Dorris The relationship between saccadic choice and reaction times with manipulations of target value Journal Article In: Frontiers in Neuroscience, vol. 5, pp. 122, 2011. @article{Milstein2011, Choosing the option with the highest expected value (EV; reward probability × reward magnitude) maximizes the intake of reward under conditions of uncertainty. However, human economic choices indicate that our value calculation has a subjective component whereby probability and reward magnitude are not linearly weighted. Using a similar economic framework, our goal was to characterize how subjective value influences the generation of simple motor actions. Specifically, we hypothesized that attributes of saccadic eye movements could provide insight into how rhesus monkeys, a well-studied animal model in cognitive neuroscience, subjectively value potential visual targets. In the first experiment, monkeys were free to choose by directing a saccade toward one of two simultaneously displayed targets, each of which had an uncertain outcome. In this task, choices were more likely to be allocated toward the higher valued target. In the second experiment, only one of the two possible targets appeared on each trial. In this task, saccadic reaction times (SRTs) decreased toward the higher valued target. Reward magnitude had a much stronger influence on both choices and SRTs than probability, whose effect was observed only when reward magnitude was similar for both targets. Across EV blocks, a strong relationship was observed between choice preferences and SRTs. However, choices tended to maximize at skewed values whereas SRTs varied more continuously. Lastly, SRTs were unchanged when all reward magnitudes were 1×, 1.5×, and 2× their normal amount, indicating that saccade preparation was influenced by the relative value of the targets rather than the absolute value of any single-target. We conclude that value is not only an important factor( )for deliberative decision making in primates, but also for the selection and preparation of simple motor actions, such as saccadic eye movements. More precisely, our results indicate that, under conditions of uncertainty, saccade choices and reaction times are influenced by the relative expected subjective value of potential movements. |
Daniel Mirman; Eiling Yee; Sheila E. Blumstein; James S. Magnuson Theories of spoken word recognition deficits in Aphasia: Evidence from eye-tracking and computational modeling Journal Article In: Brain and Language, vol. 117, no. 2, pp. 53–68, 2011. @article{Mirman2011, We used eye-tracking to investigate lexical processing in aphasic participants by examining the fixation time course for rhyme (e.g., carrot-. parrot) and cohort (e.g., beaker-. beetle) competitors. Broca's aphasic participants exhibited larger rhyme competition effects than age-matched controls. A re-analysis of previously reported data (Yee, Blumstein, & Sedivy, 2008) confirmed that Wernicke's aphasic participants exhibited larger cohort competition effects. Individual-level analyses revealed a negative correlation between rhyme and cohort competition effect size across both groups of aphasic participants. Computational model simulations were performed to examine which of several accounts of lexical processing deficits in aphasia might account for the observed effects. Simulation results revealed that slower deactivation of lexical competitors could account for increased cohort competition in Wernicke's aphasic participants; auditory perceptual impairment could account for increased rhyme competition in Broca's aphasic participants; and a perturbation of a parameter controlling selection among competing alternatives could account for both patterns, as well as the correlation between the effects. In light of these simulation results, we discuss theoretical accounts that have the potential to explain the dynamics of spoken word recognition in aphasia and the possible roles of anterior and posterior brain regions in lexical processing and cognitive control. |
Hironori Nakatani; Nicoletta Orlandi; Cees Van Leeuwen Precisely timed oculomotor and parietal EEG activity in perceptual switching Journal Article In: Cognitive Neurodynamics, vol. 5, no. 4, pp. 399–409, 2011. @article{Nakatani2011, Blinks and saccades cause transient interruptions of visual input. To investigate how such effects influence our perceptual state, we analyzed the time courses of blink and saccade rates in relation to perceptual switching in the Necker cube. Both time courses of blink and saccade rates showed peaks at different moments along the switching process. A peak in blinking rate appeared 1,000 ms prior to the switching responses. Blinks occurring around this peak were associated with subsequent switching to the preferred interpretation of the Necker cube. Saccade rates showed a peak 150 ms prior to the switching response. The direction of saccades around this peak was predictive of the perceived orientation of the Necker cube afterwards. Peak blinks were followed and peak saccades were preceded by transient parietal theta band activity indicating the changing of the perceptual interpretation. Precisely-timed blinks, therefore, can initiate perceptual switching, and precisely-timed saccades can facilitate an ongoing change of interpretation. © 2011 The Author(s). |
Nicole Naue; Daniel Strüber; Ingo Fründ; Jeanette Schadow; Daniel Lenz; Stefan Rach; Ursula Körner; Christoph S. Herrmann Gamma in motion: Pattern reversal elicits stronger gamma-band responses than motion Journal Article In: NeuroImage, vol. 55, no. 2, pp. 808–817, 2011. @article{Naue2011, Previous studies showed higher gamma-band responses (GBRs, ≈ 40. Hz) of the electroencephalogram (EEG) for moving compared to stationary stimuli. However, it is unclear whether this modulation by motion reflects a special responsiveness of the GBR to the stimulus feature ''motion,'' or whether GBR enhancements of similar magnitude can be elicited also by a salient change within a static stimulus that does not include motion.Therefore, we measured the EEG of healthy subjects watching stationary square wave gratings of high contrast that either started to move or reversed their black and white pattern shortly after their onset. The strong contrast change of the pattern reversal represented a salient but motionless change within the grating that was compared to the onset of the stationary grating and the motion onset. Induced and evoked GBRs were analyzed for all three display conditions. In order to assess the influenceof fixational eye movements on the induced GBRs, we also examined the time courses of microsaccade rates during the three display conditions. Amplitudes of both evoked and induced GBRs were stronger for pattern reversal than for motion onset. There was no significant amplitude difference between the onsets of the stationary and moving gratings. However, mean frequencies of the induced GBR were ~10. Hz higher in response to the onsets of moving compared to stationary gratings. Furthermore, the modulations of the induced GBR did not parallel the modulations of microsaccade rate, indicating that our induced GBRs reflect neuronal processes. These results suggest that, within the gamma-band range, the encoding of moving gratings in early visual cortex is primarily based on an upward frequency shift, whereas contrast changes within static gratings are reflected by amplitude enhancement. |
Mark B. Neider; Arthur F. Kramer Older adults capitalize on contextual information to guide search Journal Article In: Experimental Aging Research, vol. 37, no. 5, pp. 539–571, 2011. @article{Neider2011, Much has been learned about the age-related cognitive declines associated with the attentional processes that utilize perceptual features during visual search. However, questions remain regarding the ability of older adults to use scene information to guide search processes, perhaps as a compensatory mechanism for declines in perceptual processes. The authors had younger and older adults search pseudorealistic scenes for targets with strong or no spatial associations. Both younger and older adults exhibited reaction time benefits when searching for a target that was associated with a specific scene region. Eye movement analyses revealed that all observers dedicated most oftheir time to scanning target-consistent display regions and that guidance to these regions was often evident on the initial saccade ofa trial. Both the benefits and costs related to contextual information were larger for older adults, suggesting that this information was relied on heavily to guide search processes towards the target. |