All EyeLink Eye Tracker Publications
All 13,000+ peer-reviewed EyeLink research publications up until 2024 (with some early 2025s) 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!
2018 |
Jorrig Vogels; Vera Demberg; Jutta Kray The index of cognitive activity as a measure of cognitive processing load in dual task settings Journal Article In: Frontiers in Psychology, vol. 9, pp. 2276, 2018. @article{Vogels2018,Increases in pupil size have long been used as an indicator of cognitive load. Recently, the Index of Cognitive Activity (ICA), a novel pupillometric measure has received increased attention. The ICA measures the frequency of rapid pupil dilations, and is an interesting complementary measure to overall pupil size because it disentangles the pupil response to cognitive activity from effects of light input. As such, it has been evaluated as a useful measure of processing load in dual task settings coordinating language comprehension and driving. However, the cognitive underpinnings of pupillometry, and any differences between rapid small dilations as measured by the ICA and overall effects on pupil size are still poorly understood. Earlier work has observed that the ICA and overall pupil size may not always behave in the same way, reporting an increase in overall pupil size but decrease in ICA in a dual task setting. To further investigate this, we systematically tested two new dual-task combinations, combining both language comprehension and simulated driving with a memory task. Our findings confirm that more difficult linguistic processing is reflected in a larger ICA. More importantly, however, the dual task settings did not result in an increase in the ICA as compared to the single task, and, consistent with earlier findings, showed a significant decrease with a more difficult secondary task. This contrasts with our findings for pupil size, which showed an increase with greater secondary task difficulty in both tasks. Our results are compatible with the idea that although both pupillometry measures are indicators of cognitive load, they reflect different cognitive and neuronal processes in dual task situations. |
Joanne C. Van Slooten; Sara Jahfari; Tomas Knapen; Jan Theeuwes How pupil responses track value-based decision-making during and after reinforcement learning Journal Article In: PLoS Computational Biology, vol. 14, no. 11, pp. e1006632, 2018. @article{VanSlooten2018,Cognition can reveal itself in the pupil, as latent cognitive processes map onto specific pupil responses. For instance, the pupil dilates when we make decisions and these pupil size fluctuations reflect decision-making computations during and after a choice. Surprisingly little is known, however, about how pupil responses relate to decisions driven by the learned value of stimuli. This understanding is important, as most real-life decisions are guided by the outcomes of earlier choices. The goal of this study was to investigate which cognitive processes the pupil reflects during value-based decision-making. We used a reinforcement learning task to study pupil responses during value-based decisions and subsequent decision evaluations, employing computational modeling to quantitatively describe the underlying cognitive processes. We found that the pupil closely tracks reinforcement learning processes independently across participants and across trials. Prior to choice, the pupil dilated as a function of trial-by-trial fluctuations in value beliefs about the to-be chosen option and predicted an individual's tendency to exploit high value options. After feedback a biphasic pupil response was observed, the amplitude of which correlated with participants' learning rates. Furthermore, across trials, early feedback-related dilation scaled with value uncertainty, whereas later constriction scaled with signed reward prediction errors. These findings show that pupil size fluctuations can provide detailed information about the computations underlying value-based decisions and the subsequent updating of value beliefs. As these processes are affected in a host of psychiatric disorders, our results indicate that pupillometry can be used as an accessible tool to non-invasively study the processes underlying ongoing reinforcement learning in the clinic. |
Marco Turi; David C. Burr; Paola Binda Pupillometry reveals perceptual differences that are tightly linked to autistic traits in typical adults Journal Article In: eLife, vol. 7, pp. 1–15, 2018. @article{Turi2018,The pupil is primarily regulated by prevailing light levels but is also modulated by perceptual and attentional factors. We measured pupil-size in typical adult humans viewing a bistable-rotating cylinder, constructed so the luminance of the front surface changes with perceived direction of rotation. In some participants, pupil diameter oscillated in phase with the ambiguous perception, more dilated when the black surface was in front. Importantly, the magnitude of oscillation predicts autistic traits of participants, assessed by the Autism-Spectrum Quotient AQ. Further experiments suggest that these results are driven by differences in perceptual styles: high AQ participants focus on the front surface of the rotating cylinder, while those with low AQ distribute attention to both surfaces in a more global, holistic style. This is the first evidence that pupillometry reliably tracks inter-individual differences in perceptual styles; it does so quickly and objectively, without interfering with spontaneous perceptual strategies. |
Max Schneider; Laura Leuchs; Michael Czisch; Philipp G. Sämann; Victor I. Spoormaker Disentangling reward anticipation with simultaneous pupillometry / fMRI Journal Article In: NeuroImage, vol. 178, pp. 11–22, 2018. @article{Schneider2018,The reward system may provide an interesting intermediate phenotype for anhedonia in affective disorders. Reward anticipation is characterized by an increase in arousal, and previous studies have linked the anterior cingulate cortex (ACC) to arousal responses such as dilation of the pupil. Here, we examined pupil dynamics during a reward anticipation task in forty-six healthy human subjects and evaluated its neural correlates using functional magnetic resonance imaging (fMRI). Pupil size showed a strong increase during monetary reward anticipation, a moderate increase during verbal reward anticipation and a decrease during control trials. For fMRI analyses, average pupil size and pupil change were computed in 1-s time bins during the anticipation phase. Activity in the ventral striatum was inversely related to the pupil size time course, indicating an early onset of activation and a role in reward prediction processing. Pupil dilations were linked to increased activity in the salience network (dorsal ACC and bilateral insula), which likely triggers an increase in arousal to enhance task performance. Finally, increased pupil size preceding the required motor response was associated with activity in the ventral attention network. In sum, pupillometry provides an effective tool for disentangling different phases of reward anticipation, with relevance for affective symptomatology. |
Anne Reuten; Maureen Dam; Marnix Naber Pupillary responses to robotic and human emotions: The uncanny valley and media equation confirmed Journal Article In: Frontiers in Psychology, vol. 9, pp. 774, 2018. @article{Reuten2018,Physiological responses during human-robots interaction are useful alternatives to subjective measures of uncanny feelings for nearly humanlike robots (uncanny valley) and comparable emotional responses between humans and robots (media equation). However, no studies have employed the easily accessible measure of pupillometry to confirm the uncanny valley and media equation hypotheses, evidence in favor of the existence of these hypotheses in interaction with emotional robots is scarce, and previous studies have not controlled for low level image statistics across robot appearances. We therefore recorded pupil size of 40 participants that viewed and rated pictures of robotic and human faces that expressed a variety of basic emotions. The robotic faces varied along the dimension of human likeness from cartoonish to humanlike. We strictly controlled for confounding factors by removing backgrounds, hair, and color, and by equalizing low level image statistics. After the presentation phase, participants indicated to what extent the robots appeared uncanny and humanlike, and whether they could imagine social interaction with the robots in real life situations. The results show that robots rated as nearly humanlike scored higher on uncanniness, scored lower on imagined social interaction, evoked weaker pupil dilations, and their emotional expressions were more difficult to recognize. Pupils dilated most strongly to negative expressions and the pattern of pupil responses across emotions was highly similar between robot and human stimuli. These results highlight the usefulness of pupillometry in emotion studies and robot design by confirming the uncanny valley and media equation hypotheses. |
Eliska Prochazkova; Luisa Prochazkova; Michael Rojek Giffin; H. Steven Scholte; Carsten K. W. De Dreu; Mariska E. Kret Pupil mimicry promotes trust through the theory-of-mind network Journal Article In: Proceedings of the National Academy of Sciences, vol. 115, no. 31, pp. E7265–E7274, 2018. @article{Prochazkova2018,The human eye can provide powerful insights into the emotions and intentions of others; however, how pupillary changes influence observers' behavior remains largely unknown. The present fMRI–pupillometry study revealed that when the pupils of interacting partners synchronously dilate, trust is promoted, which suggests that pupil mimicry affiliates people. Here we provide evidence that pupil mimicry modulates trust decisions through the activation of the theory-of-mind network (precuneus, temporo-parietal junction, superior temporal sulcus, and medial prefrontal cortex). This network was recruited during pupil-dilation mimicry compared with interactions without mimicry or compared with pupil-constriction mimicry. Furthermore, the level of theory-of-mind engagement was proportional to individual's susceptibility to pupil-dilation mimicry. These data reveal a fundamental mechanism by which an individual's pupils trigger neurophysiological responses within an observer: when interacting partners synchronously dilate their pupils, humans come to feel reflections of the inner states of others, which fosters trust formation. |
Daniel R. McCloy; Eric D. Larson; Adrian K. C. Lee Auditory attention switching with listening difficulty: Behavioral and pupillometric measures Journal Article In: The Journal of the Acoustical Society of America, vol. 144, no. 5, pp. 2764–2771, 2018. @article{McCloy2018,Pupillometry has emerged as a useful tool for studying listening effort. Past work involving listeners with normal audiological thresholds has shown that switching attention between competing talker streams evokes pupil dilation indicative of listening effort [McCloy, Lau, Larson, Pratt, and Lee (2017). J. Acoust. Soc. Am. 141(4), 2440–2451]. The current experiment examines behavioral and pupillometric data from a two-stream target detection task requiring attention-switching between auditory streams, in two participant groups: audiometrically normal listeners who self-report difficulty localizing sound sources and/or understanding speech in reverberant or acoustically crowded environments, and their age-matched controls who do not report such problems. Three experimental conditions varied the number and type of stream segregation cues available. Participants who reported listening difficulty showed both behavioral and pupillometric signs of increased effort compared to controls, especially in trials where only a single stream segregation cue was available |
Sebastiaan Mathôt; Jasper H. Fabius; Elle Van Heusden; Stefan Van der Stigchel Safe and sensible preprocessing and baseline correction of pupil-size data Journal Article In: Behavior Research Methods, vol. 50, no. 1, pp. 94–106, 2018. @article{Mathot2018,Measurement of pupil size (pupillometry) has recently gained renewed interest from psychologists, but there is little agreement on how pupil-size data is best analyzed. Here we focus on one aspect of pupillometric analyses: baseline correction, i.e., analyzing changes in pupil size relative to a baseline period. Baseline correction is useful in experiments that investigate the effect of some experimental manipulation on pupil size. In such experiments, baseline correction improves statistical power by taking into account random fluctuations in pupil size over time. However, we show that baseline correction can also distort data if unrealistically small pupil sizes are recorded during the baseline period, which can easily occur due to eye blinks, data loss, or other distortions. Divisive baseline correction (corrected pupil size = pupil size/baseline) is affected more strongly by such distortions than subtractive baseline correction (corrected pupil size = pupil size - baseline). We discuss the role of baseline correction as a part of preprocessing of pupillometric data, and make five recommendations: (1) before baseline correction, perform data preprocessing to mark missing and invalid data, but assume that some distortions will remain in the data; (2) use subtractive baseline correction; (3) visually compare your corrected and uncorrected data; (4) be wary of pupil-size effects that emerge faster than the latency of the pupillary response allows (within ±220 ms after the manipulation that induces the effect); and (5) remove trials on which baseline pupil size is unrealistically small (indicative of blinks and other distortions). |
Katja I. Häuser; Vera Demberg; Jutta Kray In: Psychology and Aging, vol. 33, no. 8, pp. 1168–1180, 2018. @article{Haeuser2018,Even though older adults are known to have difficulty at language processing when a secondary task has to be performed simultaneously, few studies have addressed how older adults process language in dual-task demands when linguistic load is systematically varied. Here, we manipulated surprisal, an information theoretic measure that quantifies the amount of new information conveyed by a word, to investigate how linguistic load affects younger and older adults during early and late stages of sentence processing under conditions when attention is split between two tasks. In high-surprisal sentences, target words were implausible and mismatched with semantic expectancies based on context, thereby causing integration difficulty. Participants performed semantic meaningfulness judgments on sentences that were presented in isolation (single task) or while performing a secondary tracking task (dual task). Cognitive load was measured by means of pupillometry. Mixed-effects models were fit to the data, showing the following: (a) During the dual task, younger but not older adults demonstrated early sensitivity to surprisal (higher levels of cognitive load, indexed by pupil size) as sentences were heard online; (b) Older adults showed no immediate reaction to surprisal, but a delayed response, where their meaningfulness judgments to high-surprisal words remained stable in accuracy, while secondary tracking performance declined. Findings are discussed in relation to age-related trade-offs in dual tasking and differences in the allocation of attentional resources during language processing. Collectively, our data show that higher linguistic load leads to task trade-offs in older adults and differently affects the time course of online language processing in aging. |
Lauren K. Fink; Brian K. Hurley; Joy J. Geng; Petr Janata A linear oscillator model predicts dynamic temporal attention and pupillary entrainment to rhythmic patterns Journal Article In: Journal of Eye Movement Research, vol. 11, no. 2, pp. 1–25, 2018. @article{Fink2018,Rhythm is a ubiquitous feature of music that induces specific neural modes of processing. In this paper, we assess the potential of a stimulus-driven linear oscillator model (Tomic & Janata, 2008) to predict dynamic attention to complex musical rhythms on an instant-by-instant basis. We use perceptual thresholds and pupillometry as attentional indices against which to test our model predictions. During a deviance detection task, participants listened to continuously looping, multi-instrument, rhythmic patterns, while being eye-tracked. Their task was to respond anytime they heard an increase in intensity (dB SPL). An adaptive thresholding algorithm adjusted deviant intensity at multiple probed temporal locations throughout each rhythmic stimulus. The oscillator model predicted participants' perceptual thresholds for detecting deviants at probed locations, with a low temporal salience prediction corresponding to a high perceptual threshold and vice versa. A pupil dilation response was observed for all deviants. Notably, the pupil dilated even when partic- ipants did not report hearing a deviant. Maximum pupil size and resonator model output were significant predictors of whether a deviant was detected or missed on any given trial. Besides the evoked pupillary response to deviants, we also assessed the continuous pupillary signal to the rhythmic patterns. The pupil exhibited entrainment at prominent periodicities present in the stimuli and followed each of the different rhythmic patterns in a unique way. Overall, these results replicate previous studies using the linear oscillator model to predict dynamic attention to complex auditory scenes and extend the utility of the model to the prediction of neurophysiological signals, in this case the pupillary time course; however, we note that the amplitude envelope of the acoustic patterns may serve as a similarly useful predictor. To our knowledge, this is the first paper to show entrainment of pupil dynamics by demonstrating a phase relationship between musical stimuli and the pupillary signal. |
Garvin Brod; Marcus Hasselhorn; Silvia A. Bunge When generating a prediction boosts learning: The element of surprise Journal Article In: Learning and Instruction, vol. 55, pp. 22–31, 2018. @article{Brod2018,Using both behavioral and eye-tracking methodology, we tested whether and how asking students to generate predictions is an efficient technique to improve learning. In particular, we designed two tasks to test whether the surprise induced by outcomes that violate expectations enhances learning. Data from the first task revealed that asking participants to generate predictions, as compared to making post hoc evaluations, facilitated acquisition of geography knowledge. Pupillometry measurements revealed that expectancy-violating outcomes led to a surprise response only when a prediction was made beforehand, and that the strength of this response was positively related to the amount of learning. Data from the second task demonstrated that making predictions about the outcomes of soccer matches specifically improved memory for expectancy-violating events. These results suggest that a specific benefit of making predictions in learning contexts is that it creates the opportunity for the learner to be surprised. Implications for theory and educational practice are discussed. |
Giulia Borghini; Valerie Hazan Listening effort during sentence processing is increased for non-native listeners: A pupillometry study Journal Article In: Frontiers in Neuroscience, vol. 12, pp. 152, 2018. @article{Borghini2018,Current evidence demonstrates that even though some non-native listeners can achieve native-like performance for speech perception tasks in quiet, the presence of a background noise is much more detrimental to speech intelligibility for non-native compared to native listeners. Even when performance is equated across groups, it is likely that greater listening effort is required for non-native listeners. Importantly, the added listening effort might result in increased fatigue and a reduced ability to successfully perform multiple tasks simultaneously. Task-evoked pupil responses have been demonstrated to be a reliable measure of cognitive effort and can be useful in clarifying those aspects. In this study we compared the pupil response for 23 native English speakers and 27 Italian speakers of English as a second language. Speech intelligibility was tested for sentences presented in quiet and in background noise at two performance levels that were matched across groups. Signal-to-noise levels corresponding to these sentence intelligibility levels were pre-determined using an adaptive intelligibility task. Pupil response was significantly greater in non-native compared to native participants across both intelligibility levels. Therefore, for a given intelligibility level, a greater listening effort is required when listening in a second language in order to understand speech in noise. Results also confirmed that pupil response is sensitive to speech intelligibility during language comprehension, in line with previous research. However, contrary to our predictions, pupil response was not differentially modulated by intelligibility levels for native and non-native listeners. The present study corroborates that pupillometry can be deemed as a valid measure to be used in speech perception investigation, because it is sensitive to differences both across participants, such as listener type, and across conditions, such as variations in the level of speech intelligibility. Importantly, pupillometry offers us the possibility to uncover differences in listening effort even when those do not emerge in the performance level of individuals. |
Vladislav Ayzenberg; Meghan R. Hickey; Stella F. Lourenco Pupillometry reveals the physiological underpinnings of the aversion to holes Journal Article In: PeerJ, vol. 6, pp. 1–19, 2018. @article{Ayzenberg2018,An unusual, but common, aversion to images with clusters of holes is known as trypophobia. Recent research suggests that trypophobic reactions are caused by visual spectral properties also present in aversive images of evolutionary threatening animals (e.g., snakes and spiders). However, despite similar spectral properties, it remains unknown whether there is a shared emotional response to holes and threatening animals. Whereas snakes and spiders are known to elicit a fear reaction, associated with the sympathetic nervous system, anecdotal reports from self-described trypophobes suggest reactions more consistent with disgust, which is associated with activation of the parasympathetic nervous system. Here we used pupillometry in a novel attempt to uncover the distinct emotional response associated with a trypophobic response to holes. Across two experiments, images of holes elicited greater constriction compared to images of threatening animals and neutral images. Moreover, this effect held when controlling for level of arousal and accounting for the pupil grating response. This pattern of pupillary response is consistent with involvement of the parasympathetic nervous system and suggests a disgust, not a fear, response to images of holes. Although general aversion may be rooted in shared visual-spectral properties, we propose that the specific emotion is determined by cognitive appraisal of the distinct image content. |
Nicolai D. Ayasse; Arthur Wingfield A tipping point in listening effort: Effects of linguistic complexity and age-related hearing loss on sentence comprehension Journal Article In: Trends in Hearing, vol. 22, 2018. @article{Ayasse2018,In recent years, there has been a growing interest in the relationship between effort and performance. Early formulations implied that, as the challenge of a task increases, individuals will exert more effort, with resultant maintenance of stable performance. We report an experiment in which normal-hearing young adults, normal-hearing older adults, and older adults with age-related mild-to-moderate hearing loss were tested for comprehension of recorded sentences that varied the comprehension challenge in two ways. First, sentences were constructed that expressed their meaning either with a simpler subject-relative syntactic structure or a more computationally demanding object-relative structure. Second, for each sentence type, an adjectival phrase was inserted that created either a short or long gap in the sentence between the agent performing an action and the action being performed. The measurement of pupil dilation as an index of processing effort showed effort to increase with task difficulty until a difficulty tipping point was reached. Beyond this point, the measurement of pupil size revealed a commitment of effort by the two groups of older adults who failed to keep pace with task demands as evidenced by reduced comprehension accuracy. We take these pupillometry data as revealing a complex relationship between task difficulty, effort, and performance that might not otherwise appear from task performance alone. |
2017 |
Mahiko Konishi; Kevin Brown; Luca Battaglini; Jonathan Smallwood When attention wanders: Pupillometric signatures of fluctuations in external attention Journal Article In: Cognition, vol. 168, pp. 16–26, 2017. @article{Konishi2017,Attention is not always directed to events in the external environment. On occasion our thoughts wander to people and places distant from the here and now. Sometimes, this lack of external attention can compromise ongoing task performance. In the current study we set out to understand the extent to which states of internal and external attention can be determined using pupillometry as an index of ongoing cognition. In two experiments we found that periods of slow responding were associated with elevations in the baseline pupil signal over three and a half seconds prior to a behavioural response. In the second experiment we found that unlike behavioural lapses, states of off-task thought, particularly those associated with a focus on the past and with an intrusive quality, were associated with reductions in the size of the pupil over the same window prior to the probe. These data show that both states of large and small baseline pupil size are linked to states when attention is not effectively focused on the external environment, although these states have different qualities. More generally, these findings illustrate that subjective and objective markers of task performance may not be equivalent and underscore the importance of developing objective indicators that can allow these different states to be understood. |
Alejandra Vasquez-Rosati; Enzo P. Brunetti; Carmen Cordero; Pedro E. Maldonado Pupillary response to negative emotional stimuli is differentially affected in meditation practitioners Journal Article In: Frontiers in Human Neuroscience, vol. 11, pp. 209, 2017. @article{VasquezRosati2017,Clinically, meditative practices have become increasingly relevant, decreasing anxiety in patients and increasing antibody production. However, few studies have examined the physiological correlates, or effects of the incorporation of meditative practices. Because pupillary reactivity is a marker for autonomic changes and emotional processing, we hypothesized that the pupillary responses of mindfulness meditation practitioners (MP) and subjects without such practices (NM differ, reflecting different emotional processing. In a group of 11 MP and 9 NM, we recorded the pupil diameter using video-oculography while subjects explored images with emotional contents. Although both groups showed a similar pupillary response for positive and neutral images, negative images evoked a greater pupillary contraction and a weaker dilation in the MP group. Also, this group had faster physiological recovery to baseline levels. These results suggest that mindfulness meditation practices modulate the response of the autonomic nervous system, reflected in the pupillary response to negative images and faster physiological recovery to baseline levels, suggesting that pupillometry could be used to assess the potential health benefits of these practices in patients. |
Martina Starc; Alan Anticevic; Grega Repovš Fine-grained versus categorical: Pupil size differentiates between strategies for spatial working memory performance Journal Article In: Psychophysiology, vol. 54, no. 5, pp. 724–735, 2017. @article{Starc2017,Pupillometry provides an accessible option to track working memory processes with high temporal resolution. Several studies showed that pupil size increases with the number of items held in working memory; however, no study has explored whether pupil size also reflects the quality of working memory representations. To address this question, we used a spatial working memory task to investigate the relationship of pupil size with spatial precision of responses and indicators of reliance on generalized spatial categories. We asked 30 participants (15 female, aged 19–31) to remember the position of targets presented at various locations along a hidden radial grid. After a delay, participants indicated the remembered location with a high-precision joystick providing a parametric measure of trial-to-trial accuracy. We recorded participants' pupil dilations continuously during task performance. Results showed a significant relation between pupil dilation during preparation/early encoding and the precision of responses, possibly reflecting the attentional resources devoted to memory encoding. In contrast, pupil dilation at late maintenance and response predicted larger shifts of responses toward prototypical locations, possibly reflecting larger reliance on categorical representation. On an intraindividual level, smaller pupil dilations during encoding predicted larger dilations during late maintenance and response. On an interindividual level, participants relying more on categorical representation also produced larger precision errors. The results confirm the link between pupil size and the quality of spatial working memory representation. They suggest compensatory strategies of spatial working memory performance—loss of precise spatial representation likely increases reliance on generalized spatial categories. |
Kelly Miles; Catherine M. McMahon; Isabelle Boisvert; Ronny Ibrahim; Peter Lissa; Petra L. Graham; Björn Lyxell Objective assessment of listening effort: Coregistration of pupillometry and EEG Journal Article In: Trends in Hearing, vol. 21, 2017. @article{Miles2017,Listening to speech in noise is effortful, particularly for people with hearing impairment. While it is known that effort is related to a complex interplay between bottom-up and top-down processes, the cognitive and neurophysiological mechan-isms contributing to effortful listening remain unknown. Therefore, a reliable physiological measure to assess effort remains elusive. This study aimed to determine whether pupil dilation and alpha power change, two physiological measures suggested to index listening effort, assess similar processes. Listening effort was manipulated by parametrically varying spectral reso-lution (16-and 6-channel noise vocoding) and speech reception thresholds (SRT; 50% and 80%) while 19 young, normal-hearing adults performed a speech recognition task in noise. Results of off-line sentence scoring showed discrepancies between the target SRTs and the true performance obtained during the speech recognition task. For example, in the SRT80% condition, participants scored an average of 64.7%. Participants' true performance levels were therefore used for subsequent statistical modelling. Results showed that both measures appeared to be sensitive to changes in spectral reso-lution (channel vocoding), while pupil dilation only was also significantly related to their true performance levels (%) and task accuracy (i.e., whether the response was correctly or partially recalled). The two measures were not correlated, suggesting they each may reflect different cognitive processes involved in listening effort. This combination of findings contributes to a growing body of research aiming to develop an objective measure of listening effort. |
Ronan McGarrigle; Piers Dawes; Andrew J. Stewart; Stefanie E. Kuchinsky; Kevin J. Munro Pupillometry reveals changes in physiological arousal during a sustained listening task Journal Article In: Psychophysiology, vol. 54, no. 2, pp. 193–203, 2017. @article{McGarrigle2017a,Hearing loss is associated with anecdotal reports of fatigue during periods of sustained listening. However, few studies have attempted to measure changes in arousal, as a potential marker of fatigue, over the course of a sustained listening task. The present study aimed to examine subjective, behavioral, and physiological indices of listening-related fatigue. Twenty-four normal-hearing young adults performed a speech-picture verification task in different signal-to-noise ratios (SNRs) while their pupil size was monitored and response times recorded. Growth curve analysis revealed a significantly steeper linear decrease in pupil size in the more challenging SNR, but only in the second half of the trial block. Changes in pupil dynamics over the course of the more challenging listening condition block suggest a reduction in physiological arousal. Behavioral and self-report measures did not reveal any differences between listening conditions. This is the first study to show reduced physiological arousal during a sustained listening task, with changes over time consistent with the onset of fatigue. |
Ronan McGarrigle; Piers Dawes; Andrew J. Stewart; Stefanie E. Kuchinsky; Kevin J. Munro Measuring listening-related effort and fatigue in school-aged children using pupillometry Journal Article In: Journal of Experimental Child Psychology, vol. 161, pp. 95–112, 2017. @article{McGarrigle2017,Stress and fatigue from effortful listening may compromise well-being, learning, and academic achievement in school-aged children. The aim of this study was to investigate the effect of a signal-to-noise ratio (SNR) typical of those in school classrooms on listening effort (behavioral and pupillometric) and listening-related fatigue (self-report and pupillometric) in a group of school-aged children. A sample of 41 normal-hearing children aged 8–11 years performed a narrative speech–picture verification task in a condition with recommended levels of background noise (“ideal”: +15 dB SNR) and a condition with typical classroom background noise levels (“typical”: −2 dB SNR). Participants showed increased task-evoked pupil dilation in the typical listening condition compared with the ideal listening condition, consistent with an increase in listening effort. No differences were found between listening conditions in terms of performance accuracy and response time on the behavioral task. Similarly, no differences were found between listening conditions in self-report and pupillometric markers of listening-related fatigue. This is the first study to (a) examine listening-related fatigue in children using pupillometry and (b) demonstrate physiological evidence consistent with increased listening effort while listening to spoken narratives despite ceiling-level task performance accuracy. Understanding the physiological mechanisms that underpin listening-related effort and fatigue could inform intervention strategies and ultimately mitigate listening difficulties in children. |
Daniel R. McCloy; Bonnie K. Lau; Eric D. Larson; Katherine A. I. Pratt; Adrian K. C. Lee Pupillometry shows the effort of auditory attention switching Journal Article In: The Journal of the Acoustical Society of America, vol. 141, no. 4, pp. 2440–2451, 2017. @article{McCloy2017,© 2017 Acoustical Society of America. Successful speech communication often requires selective attention to a target stream amidst competing sounds, as well as the ability to switch attention among multiple interlocutors. However, auditory attention switching negatively affects both target detection accuracy and reaction time, suggesting that attention switches carry a cognitive cost. Pupillometry is one method of assessing mental effort or cognitive load. Two experiments were conducted to determine whether the effort associated with attention switches is detectable in the pupillary response. In both experiments, pupil dilation, target detection sensitivity, and reaction time were measured; the task required listeners to either maintain or switch attention between two concurrent speech streams. Secondary manipulations explored whether switch-related effort would increase when auditory streaming was harder. In experiment 1, spatially distinct stimuli were degraded by simulating reverberation (compromising across-time streaming cues), and target-masker talker gender match was also varied. In experiment 2, diotic streams separable by talker voice quality and pitch were degraded by noise vocoding, and the time alloted for mid-trial attention switching was varied. All trial manipulations had some effect on target detection sensitivity and/or reaction time; however, only the attention-switching manipulation affected the pupillary response: greater dilation was observed in trials requiring switching attention between talkers. |
Laura Leuchs; Max Schneider; Michael Czisch; Victor I. Spoormaker Neural correlates of pupil dilation during human fear learning Journal Article In: NeuroImage, vol. 147, pp. 186–197, 2017. @article{Leuchs2017,Background: Fear conditioning and extinction are prevailing experimental and etiological models for normal and pathological anxiety. Pupil dilations in response to conditioned stimuli are increasingly used as a robust psychophysiological readout of fear learning, but their neural correlates remain unknown. We aimed at identifying the neural correlates of pupil responses to threat and safety cues during a fear learning task. Methods: Thirty-four healthy subjects underwent a fear conditioning and extinction paradigm with simultaneous functional magnetic resonance imaging (fMRI) and pupillometry. After a stringent preprocessing and artifact rejection procedure, trial-wise pupil responses to threat and safety cues were entered as parametric modulations to the fMRI general linear models. Results: Trial-wise magnitude of pupil responses to both conditioned and safety stimuli correlated positively with activity in dorsal anterior cingulate cortex (dACC), thalamus, supramarginal gyrus and insula for the entire fear learning task, and with activity in the dACC during the fear conditioning phase in particular. Phasic pupil responses did not show habituation, but were negatively correlated with tonic baseline pupil diameter, which decreased during the task. Correcting phasic pupil responses for the tonic baseline pupil diameter revealed thalamic activity, which was also observed in an analysis employing a linear (declining) time modulation. Conclusion: Pupil dilations during fear conditioning and extinction provide useful readouts to track fear learning on a trial-by-trial level, particularly with simultaneous fMRI. Whereas phasic pupil responses reflect activity in brain regions involved in fear learning and threat appraisal, most prominently in dACC, tonic changes in pupil diameter may reflect changes in general arousal. |
Piril Hepsomali; Julie A. Hadwin; Simon P. Liversedge; Matthew Garner Pupillometric and saccadic measures of affective and executive processing in anxiety Journal Article In: Biological Psychology, vol. 127, pp. 173–179, 2017. @article{Hepsomali2017,Anxious individuals report hyper-arousal and sensitivity to environmental stimuli, difficulties concentrating, performing tasks efficiently and inhibiting unwanted thoughts and distraction. We used pupillometry and eye-movement measures to compare high vs. low anxious individuals hyper-reactivity to emotional stimuli (facial expressions) and subsequent attentional biases in a memory-guided pro- and antisaccade task during conditions of low and high cognitive load (short vs. long delay). High anxious individuals produced larger and slower pupillary responses to face stimuli, and more erroneous eye-movements, particularly following long delay. Low anxious individuals' pupillary responses were sensitive to task demand (reduced during short delay), whereas high anxious individuals' were not. These findings provide evidence in anxiety of enhanced, sustained and inflexible patterns of pupil responding during affective stimulus processing and cognitive load that precede deficits in task performance. |
Juan Haro; Marc Guasch; Blanca Vallès; Pilar Ferré Is pupillary response a reliable index of word recognition? Evidence from a delayed lexical decision task Journal Article In: Behavior Research Methods, vol. 49, no. 5, pp. 1930–1938, 2017. @article{Haro2017,Previous word recognition studies have shown that the pupillary response is sensitive to a word's frequency. However, such a pupillary effect may be due to the process of executing a response, instead of being an index of word processing. With the aim of exploring this possibility, we recorded the pupillary responses in two experiments involving a lexical decision task (LDT). In the first experiment, participants completed a standard LDT, whereas in the second they performed a delayed LDT. The delay in the response allowed us to compare pupil dilations with and without the response execution component. The results showed that pupillary response was modulated by word frequency in both the standard and the delayed LDT. This finding supports the reliability of using pupillometry for word recognition research. Importantly, our results also suggest that tasks that do not require a response during pupil recording lead to clearer and stronger effects. |
Marc Guasch; Pilar Ferré; Juan Haro Pupil dilation is sensitive to the cognate status of words: Further evidence for non-selectivity in bilingual lexical access Journal Article In: Bilingualism: Language and Cognition, vol. 20, no. 1, pp. 49–54, 2017. @article{Guasch2017,The cognate facilitation effect (i.e., a processing advantage for cognates compared to non-cognates) is an evidence of language non-selectivity in bilingual lexical access. Several studies using behavioral or electrophysiological measures have demonstrated that this effect is modulated by the degree of formal overlap between translations. However, it has never been tested with a psychophysiological measure such as pupillometry. In the present study we replicate the cognate facilitation effect by examining reaction times and pupil responses. Our results endorse pupillometry as a promising tool for bilingual research, and confirm the modulation of the cognate effect by the degree of formal similarity. |
Eugen Fischer; Paul E. Engelhardt Stereotypical inferences: Philosophical relevance and psycholinguistic toolkit Journal Article In: Ratio, vol. 30, no. 4, pp. 411–442, 2017. @article{Fischer2017,Stereotypes shape inferences in philosophical thought, political discourse, and everyday life. These inferences are routinely made when thinkers engage in language comprehension or production: We make them whenever we hear, read, or formulate stories, reports, philosophical case-descriptions, or premises of arguments – on virtually any topic. These inferences are largely automatic: largely unconscious, non-intentional, and effortless. Accordingly, they shape our thought in ways we can properly understand only by complementing traditional forms of philosophical analysis with experimental methods from psycholinguistics. This paper seeks, first, to bring out the wider philosophical relevance of stereotypical inference, well beyond familiar topics like gender and race. Second, we wish to provide (experimental) philosophers with a toolkit to experimentally study these ubiquitous inferences and what intuitions they may generate. This paper explains what stereotypes are (Section 1), and why they matter to current and traditional concerns in philosophy – experimental, analytic, and applied (Section 2). It then assembles a psycholinguistic toolkit and demonstrates through two studies (Sections 3–4) how potentially questionnairebased measures (plausibility-ratings) can be combined with process measures (reaction times and pupillometry) to garner evidence for specific stereotypical inferences and study when they ‘go through' and influence our thinking. |
Nathaniel T. Diede; Julie M. Bugg Cognitive effort is modulated outside of the explicit awareness of conflict frequency: Evidence from pupillometry Journal Article In: Journal of Experimental Psychology: Learning, Memory, and Cognition, vol. 43, no. 5, pp. 824–835, 2017. @article{Diede2017,Classic theories of cognitive control conceptualized controlled processes as slow, strategic, and willful, with automatic processes being fast and effortless. The context-specific proportion compatibility (CSPC) effect, the reduction in the compatibility effect in a context (e.g., location) associated with a high relative to low likelihood of conflict, challenged classic theories by demonstrating fast and flexible control that appears to operate outside of conscious awareness. Two theoretical questions yet to be addressed are whether the CSPC effect is accompanied by context-dependent variation in effort, and whether the exertion of effort depends on explicit awareness of context-specific task demands. To address these questions, pupil diameter was measured during a CSPC paradigm. Stimuli were randomly presented in either a mostly compatible location or a mostly incompatible location. Replicating prior research, the CSPC effect was found. The novel finding was that pupil diameter was greater in the mostly incompatible location compared to the mostly compatible location, despite participants' lack of awareness of context-specific task demands. Additionally, this difference occurred regardless of trial type or a preceding switch in location. These patterns support the view that context (location) dictates selection of optimal attentional settings in the CSPC paradigm, and varying levels of effort and performance accompany these settings. Theoretically, these patterns imply that cognitive control may operate fast, flexibly, and outside of awareness, but not effortlessly. |
Árni Gunnar Ásgeirsson; Sander Nieuwenhuis No arousal-biased competition in focused visuospatial attention Journal Article In: Cognition, vol. 168, pp. 191–204, 2017. @article{Asgeirsson2017,Arousal sometimes enhances and sometimes impairs perception and memory. A recent theory attempts to reconcile these findings by proposing that arousal amplifies the competition between stimulus representations, strengthening already strong representations and weakening already weak representations. Here, we report a stringent test of this arousal-biased competition theory in the context of focused visuospatial attention. Participants were required to identify a briefly presented target in the context of multiple distractors, which varied in the degree to which they competed for representation with the target, as revealed by psychophysics. We manipulated arousal using emotionally arousing pictures (Experiment 1), alerting tones (Experiment 2) and white-noise stimulation (Experiment 3), and validated these manipulations with electroencephalography and pupillometry. In none of the experiments did we find evidence that arousal modulated the effect of distractor competition on the accuracy of target identification. Bayesian statistics revealed moderate to strong evidence against arousal-biased competition. Modeling of the psychophysical data based on Bundesen's (1990) theory of visual attention corroborated the conclusion that arousal does not bias competition in focused visuospatial attention. |
2016 |
Michael W. Weiss; Sandra E. Trehub; E. Glenn Schellenberg; Peter Habashi Pupils dilate for vocal or familiar music Journal Article In: Journal of Experimental Psychology: Human Perception and Performance, vol. 42, no. 8, pp. 1061–1065, 2016. @article{Weiss2016,Previous research reveals that vocal melodies are remembered better than instrumental renditions. Here we explored the possibility that the voice, as a highly salient stimulus, elicits greater arousal than nonvocal stimuli, resulting in greater pupil dilation for vocal than for instrumental melodies. We also explored the possibility that pupil dilation indexes memory for melodies. We tracked pupil dilation during a single exposure to 24 unfamiliar folk melodies (half sung to la la, half piano) and during a subsequent recognition test in which the previously heard melodies were intermixed with 24 novel melodies (half sung, half piano) from the same corpus. Pupil dilation was greater for vocal melodies than for piano melodies in the exposure phase and in the test phase. It was also greater for previously heard melodies than for novel melodies. Our findings provide the first evidence that pupillometry can be used to measure recognition of stimuli that unfold over several seconds. They also provide the first evidence of enhanced arousal to vocal melodies during encoding and retrieval, thereby supporting the more general notion of the voice as a privileged signal. |
Basil Wahn; Daniel P. Ferris; W. David Hairston; Peter König Pupil sizes scale with attentional load and task experience in a multiple object tracking task Journal Article In: PLoS ONE, vol. 11, no. 12, pp. e0168087, 2016. @article{Wahn2016a,Previous studies have related changes in attentional load to pupil size modulations. How-ever, studies relating changes in attentional load and task experience on a finer scale to pupil size modulations are scarce. Here, we investigated how these changes affect pupil sizes. To manipulate attentional load, participants covertly tracked between zero and five objects among several randomly moving objects on a computer screen. To investigate effects of task experience, the experiment was conducted on three consecutive days. We found that pupil sizes increased with each increment in attentional load. Across days, we found systematic pupil size reductions. We compared the model fit for predicting pupil size modulations using attentional load, task experience, and task performance as predictors. We found that a model which included attentional load and task experience as predictors had the best model fit while adding performance as a predictor to this model reduced the overall model fit. Overall, results suggest that pupillometry provides a viable metric for pre-cisely assessing attentional load and task experience in visuospatial tasks. |
Anita E. Wagner; Paolo Toffanin; Deniz Baskent The timing and effort of lexical access in natural and degraded speech Journal Article In: Frontiers in Psychology, vol. 7, pp. 398, 2016. @article{Wagner2016,Understanding speech is effortless in ideal situations, and although adverse conditions, such as caused by hearing impairment, often render it an effortful task, they do not necessarily suspend speech comprehension. A prime example of this is speech perception by cochlear implant users, whose hearing prostheses transmit speech as a significantly degraded signal. It is yet unknown how mechanisms of speech processing deal with such degraded signals, and whether they are affected by effortful processing of speech. This paper compares the automatic process of lexical competition between natural and degraded speech, and combines gaze fixations, which capture the course of lexical disambiguation, with pupillometry, which quantifies the mental effort involved in processing speech. Listeners' ocular responses were recorded during disambiguation of lexical embeddings with matching and mismatching durational cues. Durational cues were selected due to their substantial role in listeners' quick limitation of the number of lexical candidates for lexical access in natural speech. Results showed that lexical competition increased mental effort in processing natural stimuli in particular in presence of mismatching cues. Signal degradation reduced listeners' ability to quickly integrate durational cues in lexical selection, and delayed and prolonged lexical competition. The effort of processing degraded speech was increased overall, and because it had its sources at the pre-lexical level this effect can be attributed to listening to degraded speech rather than to lexical disambiguation. In sum, the course of lexical competition was largely comparable for natural and degraded speech, but showed crucial shifts in timing, and different sources of increased mental effort. We argue that well-timed progress of information from sensory to pre-lexical and lexical stages of processing, which is the result of perceptual adaptation during speech development, is the reason why in ideal situations speech is perceived as an undemanding task. Degradation of the signal or the receiver channel can quickly bring this well-adjusted timing out of balance and lead to increase in mental effort. Incomplete and effortful processing at the early pre-lexical stages has its consequences on lexical processing as it adds uncertainty to the forming and revising of lexical hypotheses. |
Johanne Tromp; Peter Hagoort; Antje S. Meyer Pupillometry reveals increased pupil size during indirect request comprehension Journal Article In: Quarterly Journal of Experimental Psychology, vol. 69, no. 6, pp. 1093–1108, 2016. @article{Tromp2016,Fluctuations in pupil size have been shown to reflect variations in processing demands during lexical and syntactic processing in language comprehension. An issue that has not received attention is whether pupil size also varies due to pragmatic manipulations. In two pupillometry experiments, we investigated whether pupil diameter was sensitive to increased processing demands as a result of comprehending an indirect request versus a direct statement. Adult participants were presented with 120 picture-sentence combinations that could be interpreted either as an indirect request (a picture of a window with the sentence "it's very hot here") or as a statement (a picture of a window with the sentence "it's very nice here"). Based on the hypothesis that understanding indirect utterances requires additional inferences to be made on the part of the listener, we predicted a larger pupil diameter for indirect requests than statements. The results of both experiments are consistent with this expectation. We suggest that the increase in pupil size reflects additional processing demands for the comprehension of indirect requests as compared to statements. This research demonstrates the usefulness of pupillometry as a tool for experimental research in pragmatics. |
Max Schneider; Pamela Hathway; Laura Leuchs; Philipp G. Sämann; Michael Czisch; Victor I. Spoormaker Spontaneous pupil dilations during the resting state are associated with activation of the salience network Journal Article In: NeuroImage, vol. 139, pp. 189–201, 2016. @article{Schneider2016,Resting state functional magnetic resonance imaging (rs-fMRI) is increasingly applied for the development of functional biomarkers in brain disorders. Recent studies have revealed spontaneous vigilance drifts during the resting state, involving changes in brain activity and connectivity that challenge the validity of uncontrolled rs-fMRI findings. In a combined rs-fMRI/eye tracking study, the pupil size of 32 healthy subjects after 2 h of sleep restriction was recorded as an indirect index for activity of the locus coeruleus, the brainstem's noradrenergic arousal center. The spontaneous occurrence of pupil dilations, but not pupil size per se, was associated with increased activity of the salience network, thalamus and frontoparietal regions. In turn, spontaneous constrictions of the pupil were associated with increased activity in visual and sensorimotor regions. These results were largely replicated in a sample of 36 healthy subjects who did not undergo sleep restriction, although in this sample the correlation between thalamus and pupil dilation fell below whole-brain significance. Our data show that spontaneous pupil fluctuations during rest are indeed associated with brain circuitry involved in tonic alertness and vigilance. Pupillometry is an effective method to control for changes in tonic alertness during rs-fMRI. |
Sameer Saproo; Victor Shih; David C. Jangraw; Paul Sajda Neural mechanisms underlying catastrophic failure in human-machine interaction during aerial navigation Journal Article In: Journal of Neural Engineering, vol. 13, pp. 1–12, 2016. @article{Saproo2016,Objective. We investigated the neural correlates of workload buildup in a fine visuomotor task called the boundary avoidance task (BAT). The BAT has been known to induce naturally occurring failures of human–machine coupling in high performance aircraft that can potentially lead to a crash—these failures are termed pilot induced oscillations (PIOs). Approach. We recorded EEG and pupillometry data from human subjects engaged in a flight BAT simulated within a virtual 3D environment. Main results. We find that workload buildup in a BAT can be successfully decoded from oscillatory features in the electroencephalogram (EEG). Information in delta, theta, alpha, beta, and gamma spectral bands of the EEG all contribute to successful decoding, however gamma band activity with a lateralized somatosensory topography has the highest contribution, while theta band activity with a fronto-central topography has the most robust contribution in terms of real-world usability. We show that the output of the spectral decoder can be used to predict PIO susceptibility. We also find that workload buildup in the task induces pupil dilation, the magnitude of which is significantly correlated with the magnitude of the decoded EEG signals. These results suggest that PIOs may result from the dysregulation of cortical networks such as the locus coeruleus (LC)—anterior cingulate cortex (ACC) circuit. Significance. Our findings may generalize to similar control failures in other cases of tight manmachine coupling where gains and latencies in the control system must be inferred and compensated for by the human operators. A closed-loop intervention using neurophysiological decoding of workload buildup that targets the LC-ACC circuit may positively impact operator performance in such situations. |
Sebastiaan Mathôt; Jean-Baptiste Melmi; Lotje Linden; Stefan Van Der Stigchel The mind-writing pupil: A human-computer interface based on decoding of covert attention through pupillometry Journal Article In: PLoS ONE, vol. 11, no. 2, pp. e0148805, 2016. @article{Mathot2016,We present a new human-computer interface that is based on decoding of attention through pupillometry. Our method builds on the recent finding that covert visual attention affects the pupillary light response: Your pupil constricts when you covertly (without looking at it) attend to a bright, compared to a dark, stimulus. In our method, participants covertly attend to one of several letters with oscillating brightness. Pupil size reflects the brightness of the selected letter, which allows us–with high accuracy and in real time–to determine which letter the par- ticipant intends to select. The performance of our method is comparable to the best covert- attention brain-computer interfaces to date, and has several advantages: no movement other than pupil-size change is required; no physical contact is required (i.e. no electrodes); it is easy to use; and it is reliable. Potential applications include: communication with totally locked-in patients, training of sustained attention, and ultra-secure password input. |
Gary J. Lewis; Timothy C. Bates In: Journal of Cognitive Neuroscience, vol. 28, no. 2, pp. 308–318, 2016. @article{Lewis2016,The ability to adaptively shift between exploration and exploitation control states is critical for optimizing behavioral performance. Converging evidence from primate electrophysiology and computational neural modeling has suggested that this ability may be mediated by the broad norepinephrine projections emanating from the locus coeruleus (LC) [Aston-Jones, G., & Cohen, J. D. An integrative theory of locus coeruleus-norepinephrine function: Adaptive gain and optimal performance. Annual Review of Neuroscience, 28, 403–450, 2005]. There is also evidence that pupil diameter covaries systematically with LC activity. Although imperfect and indirect, this link makes pupillometry a useful tool for studying the locus coeruleus norepinephrine system in humans and in high-level tasks. Here, we present a novel paradigm that examines how the pupillary response during exploration and exploitation covaries with individual differences in fluid intelligence during analogical reasoning on Raven's Advanced Progressive Matrices. Pupillometry was used as a noninvasive proxy for LC activity, and concurrent think-aloud verbal protocols were used to identify exploratory and exploitative solution periods. This novel combination of pupillometry and verbal protocols from 40 participants revealed a decrease inpupil diameter during exploitation and an increase during exploration. The temporal dynamics of the pupillary response was characterized by a steep increase during the transition to exploratory periods, sustained dilation for many seconds afterward, and followed by gradual return to baseline.Moreover, the individual differences in the relative magnitude of pupillary dilation accounted for 16% of the variance in Advanced Progressive Matrices scores. Assuming that pupil diameter is a valid index of LC activity, these results establish promising preliminary connections between the literature on locus coeruleus norepinephrine-mediated cognitive control and the literature on analogical reasoning and fluid intelligence. |
Markos Kyritsis; Stephen R. Gulliver; Eva Feredoes Environmental factors and features that influence visual search in a 3D WIMP interface Journal Article In: International Journal of Human-Computer Studies, vol. 92-93, pp. 30–43, 2016. @article{Kyritsis2016,The challenge of moving past the classic Window Icons Menus Pointer (WIMP) interface, i.e. by turning it '3D', has resulted in much research and development. To evaluate the impact of 3D on the 'finding a target picture in a folder' task, we built a 3D WIMP interface that allowed the systematic manipulation of visual depth, visual aides, semantic category distribution of targets versus non-targets; and the detailed measurement of lower-level stimuli features. Across two separate experiments, one large sample web-based experiment, to understand associations, and one controlled lab environment, using eye tracking to understand user focus, we investigated how visual depth, use of visual aides, use of semantic categories, and lower-level stimuli features (i.e. contrast, colour and luminance) impact how successfully participants are able to search for, and detect, the target image. Moreover in the lab-based experiment, we captured pupillometry measurements to allow consideration of the influence of increasing cognitive load as a result of either an increasing number of items on the screen, or due to the inclusion of visual depth. Our findings showed that increasing the visible layers of depth, and inclusion of converging lines, did not impact target detection times, errors, or failure rates. Low-level features, including colour, luminance, and number of edges, did correlate with differences in target detection times, errors, and failure rates. Our results also revealed that semantic sorting algorithms significantly decreased target detection times. Increased semantic contrasts between a target and its neighbours correlated with an increase in detection errors. Finally, pupillometric data did not provide evidence of any correlation between the number of visible layers of depth and pupil size, however, using structural equation modelling, we demonstrated that cognitive load does influence detection failure rates when there is luminance contrasts between the target and its surrounding neighbours. Results suggest that WIMP interaction designers should consider stimulus-driven factors, which were shown to influence the efficiency with which a target icon can be found in a 3D WIMP interface. |
Phillip D. Fletcher; Jennifer M. Nicholas; Laura E. Downey; Hannah L. Golden; Camilla N. Clark; Carolina Pires; Jennifer L. Agustus; Catherine J. Mummery; Jonathan M. Schott; Jonathan D. Rohrer; Sebastian J. Crutch; Jason D. Warren A physiological signature of sound meaning in dementia Journal Article In: Cortex, vol. 77, pp. 13–23, 2016. @article{Fletcher2016,The meaning of sensory objects is often behaviourally and biologically salient and decoding of semantic salience is potentially vulnerable in dementia. However, it remains unclear how sensory semantic processing is linked to physiological mechanisms for coding object salience and how that linkage is affected by neurodegenerative diseases. Here we addressed this issue using the paradigm of complex sounds. We used pupillometry to compare physiological responses to real versus synthetic nonverbal sounds in patients with canonical dementia syndromes (behavioural variant frontotemporal dementia - bvFTD, semantic dementia - SD; progressive nonfluent aphasia - PNFA; typical Alzheimer's disease - AD) relative to healthy older individuals. Nonverbal auditory semantic competence was assessed using a novel within-modality sound classification task and neuroanatomical associations of pupillary responses were assessed using voxel-based morphometry (VBM) of patients' brain MR images. After taking affective stimulus factors into account, patients with SD and AD showed significantly increased pupil responses to real versus synthetic sounds relative to healthy controls. The bvFTD, SD and AD groups had a nonverbal auditory semantic deficit relative to healthy controls and nonverbal auditory semantic performance was inversely correlated with the magnitude of the enhanced pupil response to real versus synthetic sounds across the patient cohort. A region of interest analysis demonstrated neuroanatomical associations of overall pupil reactivity and differential pupil reactivity to sound semantic content in superior colliculus and left anterior temporal cortex respectively. Our findings suggest that autonomic coding of auditory semantic ambiguity in the setting of a damaged semantic system may constitute a novel physiological signature of neurodegenerative diseases. |
Federica Bianchi; Sébastien Santurette; Dorothea Wendt; Torsten Dau Pitch discrimination in musicians and non-musicians: Effects of harmonic resolvability and processing effort Journal Article In: JARO - Journal of the Association for Research in Otolaryngology, vol. 17, no. 1, pp. 69–79, 2016. @article{Bianchi2016,Musicians typically show enhanced pitch discrimination abilities compared to non-musicians. The present study investigated this perceptual enhancement behaviorally and objectively for resolved and unresolved complex tones to clarify whether the enhanced performance in musicians can be ascribed to increased peripheral frequency selectivity and/or to a different processing effort in performing the task. In a first experiment, pitch discrimination thresholds were obtained for harmonic complex tones with fundamental frequencies (F0s) between 100 and 500 Hz, filtered in either a low- or a high-frequency region, leading to variations in the resolvability of audible harmonics. The results showed that pitch discrimination performance in musicians was enhanced for resolved and unresolved complexes to a similar extent. Additionally, the harmonics became resolved at a similar F0 in musicians and non-musicians, suggesting similar peripheral frequency selectivity in the two groups of listeners. In a follow-up experiment, listeners' pupil dilations were measured as an indicator of the required effort in performing the same pitch discrimination task for conditions of varying resolvability and task difficulty. Pupillometry responses indicated a lower processing effort in the musicians versus the non-musicians, although the processing demand imposed by the pitch discrimination task was individually adjusted according to the behavioral thresholds. Overall, these findings indicate that the enhanced pitch discrimination abilities in musicians are unlikely to be related to higher peripheral frequency selectivity and may suggest an enhanced pitch representation at more central stages of the auditory system in musically trained listeners. |
2015 |
Eefje W. M. Rondeel; Henk Steenbergen; Rob W. Holland; Ad Knippenberg A closer look at cognitive control: Differences in resource allocation during updating, inhibition and switching as revealed by pupillometry Journal Article In: Frontiers in Human Neuroscience, vol. 9, pp. 494, 2015. @article{Rondeel2015,The present study investigated resource allocation, as measured by pupil dilation, in tasks measuring updating (2-Back task), inhibition (Stroop task) and switching (Number Switch task). Because each cognitive control component has unique characteristics, differences in patterns of resource allocation were expected. Pupil and behavioral data from 35 participants were analyzed. In the 2-Back task (requiring correct matching of current stimulus identity at trial p with the stimulus two trials back, p -2) we found that better performance (low total of errors made in the task) was positively correlated to the mean pupil dilation during correctly responding to targets. In the Stroop task, pupil dilation on incongruent trials was higher than those on congruent trials. Incongruent vs. congruent trial pupil dilation differences were positively related to reaction time differences between incongruent and congruent trials. Furthermore, on congruent Stroop trials, pupil dilation was negatively related to reaction times, presumably because more effort allocation paid off in terms of faster responses. In addition, pupil dilation on correctly-responded-to congruent trials predicted a weaker Stroop interference effect in terms of errors, probably because pupil dilation on congruent trials were diagnostic of task motivation, resulting in better performance. In the Number Switch task we found higher pupil dilation in switch as compared to non-switch trials. On the Number Switch task, pupil dilation was not related to performance. We also explored error-related pupil dilation in all tasks. The results provide new insights in the diversity of the cognitive control components in terms of resource allocation as a function of individual differences, task difficulty and error processing. |
Frieder M. Paulus; Sören Krach; Marius Blanke; Christine Roth; Marcus Belke; Jens Sommer; Laura Müller-Pinzler; Katja Menzler; Andreas Jansen; Felix Rosenow; Frank Bremmer; Wolfgang Einhäuser; Susanne Knake Fronto-insula network activity explains emotional dysfunctions in juvenile myoclonic epilepsy: Combined evidence from pupillometry and fMRI Journal Article In: Cortex, vol. 65, pp. 219–231, 2015. @article{Paulus2015,Emotional instability, difficulties in social adjustment, and disinhibited behavior are the most common symptoms of the psychiatric comorbidities in juvenile myoclonic epilepsy (JME). This psychopathology has been associated with dysfunctions of mesial-frontal brain circuits. The present work is a first direct test of this link and adapted a paradigm for probing frontal circuits during empathy for pain. Neural and psychophysiological parameters of pain empathy were assessed by combining functional magnetic resonance imaging (fMRI) with simultaneous pupillometry in 15 JME patients and 15 matched healthy controls. In JME patients, we observed reduced neural activation of the anterior cingulate cortex (ACC), the anterior insula (AI), and the ventrolateral prefrontal cortex (VLPFC). This modulation was paralleled by reduced pupil dilation during empathy for pain in patients. At the same time, pupil dilation was positively related to neural activity of the ACC, AI, and VLPFC. In JME patients, the ACC additionally showed reduced functional connectivity with the primary and secondary somatosensory cortex, areas fundamentally implicated in processing the somatic cause of another's pain. Our results provide first evidence that alterations of mesial-frontal circuits directly affect psychosocial functioning in JME patients and draw a link of pupil dynamics with brain activity during emotional processing. The findings of reduced pain empathy related activation of the ACC and AI and aberrant functional integration of the ACC with somatosensory cortex areas provide further evidence for this network's role in social behavior and helps explaining the JME psychopathology and patients' difficulties in social adjustment. |
Sebastiaan Mathôt; Jean-Baptiste Melmi; Eric Castet Intrasaccadic perception triggers pupillary constriction Journal Article In: PeerJ, vol. 3, pp. 1–16, 2015. @article{Mathot2015,It is commonly believed that vision is impaired during saccadic eye movements. However, here we report that some visual stimuli are clearly visible during saccades, and trigger a constriction of the eye's pupil. Participants viewed sinusoid gratings that changed polarity 150 times per second (every 6.67 ms). At this rate of flicker, the gratings were perceived as homogeneous surfaces while participants fixated. However, the flickering gratings contained ambiguous motion: rightward and leftward motion for vertical gratings; upward and downward motion for horizontal gratings. When participants made a saccade perpendicular to the gratings' orientation (e.g., a leftward saccade for a vertical grating), the eye's peak velocity matched the gratings' motion. As a result, the retinal image was approximately stable for a brief moment during the saccade, and this gave rise to an intrasaccadic percept: A normally invisible stimulus became visible when eye velocity was maximal. Our results confirm and extend previous studies by demonstrating intrasaccadic perception using a reflexive measure (pupillometry) that does not rely on subjective report. Our results further show that intrasaccadic perception affects all stages of visual processing, from the pupillary response to visual awareness. |
Sören Krach; Inge Kamp-Becker; Wolfgang Einhäuser; Jens Sommer; Stefan Frässle; Andreas Jansen; Lena Rademacher; Laura Müller-Pinzler; Valeria Gazzola; Frieder M. Paulus Evidence from pupillometry and fMRI indicates reduced neural response during vicarious social pain but not physical pain in autism Journal Article In: Human Brain Mapping, vol. 36, no. 11, pp. 4730–4744, 2015. @article{Krach2015,Autism spectrum disorder (ASD) is characterized by substantial social deficits. The notion that dysfunctions in neural circuits involved in sharing another's affect explain these deficits is appealing, but has received only modest experimental support. Here we evaluated a complex paradigm on the vicarious social pain of embarrassment to probe social deficits in ASD as to whether it is more potent than paradigms currently in use. To do so we acquired pupillometry and fMRI in young adults with ASD and matched healthy controls. During a simple vicarious physical pain task no differences emerged between groups in behavior, pupillometry, and neural activation of the anterior insula (AIC) and anterior cingulate cortex (ACC). In contrast, processing complex vicarious social pain yielded reduced responses in ASD on all physiological measures of sharing another's affect. The reduced activity within the AIC was thereby explained by the severity of autistic symptoms in the social and affective domain. Additionally, behavioral responses lacked correspondence with the anterior cingulate and anterior insula cortex activity found in controls. Instead, behavioral responses in ASD were associated with hippocampal activity. The observed dissociation echoes the clinical observations that deficits in ASD are most pronounced in complex social situations and simple tasks may not probe the dysfunctions in neural pathways involved in sharing affect. Our results are highly relevant because individuals with ASD may have preserved abilities to share another's physical pain but still have problems with the vicarious representation of more complex emotions that matter in life. |
Kai Kaspar; Vanessa Krapp; Peter König Hand washing induces a clean slate effect in moral judgments: A pupillometry and eye-tracking study Journal Article In: Scientific Reports, vol. 5, pp. 10471, 2015. @article{Kaspar2015a,Physical cleansing is commonly understood to protect us against physical contamination. However, recent studies showed additional effects on moral judgments. Under the heading of the "Macbeth effect" direct links between bodily cleansing and one's own moral purity have been demonstrated. Here we investigate (1) how moral judgments develop over time and how they are altered by hand washing, (2) whether changes in moral judgments can be explained by altered information sampling from the environment, and (3) whether hand washing affects emotional arousal. Using a pre-post control group design, we found that morality ratings of morally good and bad scenes acquired more extreme values in the control group over time, an effect that was fully counteracted by intermediate hand washing. This result supports the notion of a clean slate effect by hand washing. Thereby, eye-tracking data did not uncover differences in eye movement behavior that may explain differences in moral judgments. Thus, the clean slate effect is not due to altered information sampling from the environment. Finally, compared to the control group, pupil diameter decreased after hand washing, thus demonstrating a direct physiological effect. The results shed light on the physiological mechanisms behind this type of embodiment phenomenon. |
Nabil Hasshim; Benjamin A. Parris In: Attention, Perception, & Psychophysics, vol. 77, no. 8, pp. 2601–2610, 2015. @article{Hasshim2015,Conflict in the Stroop task is thought to come from various stages of processing, including semantics. Two-to-one response mappings, in which two response-set colors share a common response location, have been used to isolate stimulus-stimulus (semantic) from stimulus-response conflict in the Stroop task. However, the use of congruent trials as a baseline means that the measured effects could be exaggerated by facilitation, and recent research using neutral, non-color-word trials as a baseline has supported this notion. In the present study, we sought to provide evidence for stimulus-stimulus conflict using an oculomotor Stroop task and an early, preresponse pupillometric measure of effort. The results provided strong (Bayesian) evidence for no statistical difference between two-to-one response-mapping trials and neutral trials in both saccadic response latencies and preresponse pupillometric measures, supporting the notion that the difference between same-response and congruent trials indexes facilitation in congruent trials, and not stimulus-stimulus conflict, thus providing evidence against the presence of semantic conflict in the Stroop task. We also demonstrated the utility of preresponse pupillometry in measuring Stroop interference, supporting the idea that pupillary effects are not simply a residue of making a response. |
Russell Cohen Hoffing; Aaron R. Seitz Pupillometry as a glimpse into the neurochemical basis of human memory encoding Journal Article In: Journal of Cognitive Neuroscience, vol. 27, no. 4, pp. 765–774, 2015. @article{CohenHoffing2015,Neurochemical systems are well studied in animal learning; however, ethical issues limit methodologies to explore these systems in humans. Pupillometry provides a glimpse into the brain ʼs neurochemical systems, where pupil dynamics in monkeys have been linked with locus coeruleus activity, which releases norepinephrine (NE) throughout the brain. Here, we use pupil dynamics as a surrogate measure of neurochemical activity to explore the hypothesis that NE is involved in modulating memory encoding. We examine this using a task-irrelevant learning paradigm in which learning is boosted for stimuli temporally paired with task targets. We show that participants better recognize images that are paired with task targets than distractors and, in correspondence, that pupil size changes more for target-paired than distractor-paired images. To further investigate the hypothesis that NE nonspecifically guides learning for stimuli that are present with its release, a second procedure was used that employed an unexpected sound to activate the LC –NE system and induce pupil-size changes; results indicated a corresponding increase in memorization of images paired with the unexpected sounds. Together, these results suggest a relationship between the LC–NE system, pupil-size changes, and human memory encoding |
2014 |
Jennifer G. Tichon; Guy Wallis; Stephan Riek; Timothy Mavin Physiological measurement of anxiety to evaluate performance in simulation training Journal Article In: Cognition, Technology and Work, vol. 16, no. 2, pp. 203–210, 2014. @article{Tichon2014a,The ability to control emotion is a skill which contributes to performance in the same way as cognitive and technical skills do to the successful completion of high stress operations. The interdependence between emotion, problem-solving and decision-making makes a negative emotion such as anxiety of interest in evaluating trainee performance in simulations which replicate stressful work conditions. Self-report measures of anxiety require trainees to interrupt the simulation experience to either complete psychological scales or make verbal reports of state anxiety. An uninterrupted, continuous measure of anxiety is, therefore, preferable for simulation environments. During this study, the anxiety levels of trainee pilots were tracked via electromyography, eye movements and pupillometry while undertaking required tasks in a flight simulation. Fixation duration and saccade rate corresponded reliably to pilot self-reports of anxiety, while pupil size and saccade amplitude did not show a strong comparison to changes in affective state. Large increases in muscle activation where recorded when higher anxiety was reported. The results suggest that a combination of physiological measures could provide a robust, continuous indicator of anxiety level. The implications of the current study on further development of physiological measures to support tracking anxiety as a tool for simulation training assessment are discussed. © 2013 Springer-Verlag London. |
Jennifer G. Tichon; Timothy Mavin; Guy Wallis; Troy A. W. Visser; Stephan Riek Using pupillometry and electromyography to track positive and negative affect during flight simulation Journal Article In: Aviation Psychology and Applied Human Factors, vol. 4, no. 1, pp. 23–32, 2014. @article{Tichon2014,Affect is a key determinant of performance, due to its influence on cognitive processing. Negative emotions such as anxiety are recognized cognitive stressors shown to degrade decision making and situation awareness. Conversely, positive affect can improve problem solving and facilitate recall. This exploratory pilot study used electromyography and pupillometry measures to track pilots' levels of negative and positive affect while training in a flight simulator. Fixation duration and saccade rate were found to correspond reliably to pilot self-reports of anxiety. Additionally, large increases in muscle activation were also recorded when higher anxiety was reported. Decreases in positive affect correlated significantly with saccade rate, fixation duration, and mean saccade velocity. Results are discussed in terms of using psychophysiological measures to provide a continuous, objective measure of pilot affective levels as an additional evaluation method to support assessment of pilot performance in simulation training environments. |
Frederik Platten; Maximilian Schwalm; Julia Hülsmann; Josef Krems Analysis of compensative behavior in demanding driving situations Journal Article In: Transportation Research Part F: Traffic Psychology and Behaviour, vol. 26, no. A, pp. 38–48, 2014. @article{Platten2014,Drivers usually perform a range of different activities while driving. Following a classical workload approach, additional activities are expected to increase the demand on the driver. Nevertheless, drivers can usually manage even demanding situations successfully. They seem to be able to compensate demands by behavior adaptations, mainly in the following factors: in the driving task itself, in an additional (secondary) task and in their mental workload. It is suggested that by analyzing these three factors in temporal coherence, compensative interactions between them become measurable. Additionally, a reduction of activity in the secondary task is expected to be influenced by the characteristics of this task. To analyze these effects, a driving simulator study with 33 participants was accomplished. It could be shown that if a secondary task can be interrupted without a perceived decline in performance, it is interrupted in demanding driving situations. If an interruption causes a perceived performance loss, efforts are increased, and so the workload is heightened (measured with a high resolution physiological measurement based on pupillometry). Thus, drivers compensate their current demands by behavior adaptations in different factors, depending on the characteristics of a secondary task. |
Kimberly S. Chiew; Todd S. Braver Dissociable influences of reward motivation and positive emotion on cognitive control Journal Article In: Cognitive, Affective, & Behavioral Neuroscience, vol. 14, no. 2, pp. 509–529, 2014. @article{Chiew2014,It is becoming increasingly appreciated that affective and/or motivational influences contribute strongly to goal-oriented cognition and behavior. An unresolved question is whether emotional manipulations (i.e., direct induction of affectively valenced subjective experience) and motivational manipulations (e.g., delivery of performance-contingent rewards and punishments) have similar or distinct effects on cognitive control. Prior work has suggested that reward motivation can reliably enhance a proactive mode of cognitive control, whereas other evidence is suggestive that positive emotion improves cognitive flexibility, but reduces proactive control. However, a limitation of the prior research is that reward motivation and positive emotion have largely been studied independently. Here, we directly compared the effects of positive emotion and reward motivation on cognitive control with a tightly matched, within-subjects design, using the AX-continuous performance task paradigm, which allows for relative measurement of proactive versus reactive cognitive control. High-resolution pupillometry was employed as a secondary measure of cognitive dynamics during task performance. Robust increases in behavioral and pupillometric indices of proactive control were observed with reward motivation. The effects of positive emotion were much weaker, but if anything, also reflected enhancement of proactive control, a pattern that diverges from some prior findings. These results indicate that reward motivation has robust influences on cognitive control, while also highlighting the complexity and heterogeneity of positive-emotion effects. The findings are discussed in terms of potential neurobiological mechanisms. © 2014 The Author(s). |
James F. Cavanagh; Thomas V. Wiecki; Angad Kochar; Michael J. Frank Eye tracking and pupillometry are indicators of dissociable latent decision processes Journal Article In: Journal of Experimental Psychology: General, vol. 143, no. 4, pp. 1476–1488, 2014. @article{Cavanagh2014,Can you predict what people are going to do just by watching them? This is certainly difficult: it would require a clear mapping between observable indicators and unobservable cognitive states. In this report, we demonstrate how this is possible by monitoring eye gaze and pupil dilation, which predict dissociable biases during decision making. We quantified decision making using the drift diffusion model (DDM), which provides an algorithmic account of how evidence accumulation and response caution contribute to decisions through separate latent parameters of drift rate and decision threshold, respectively. We used a hierarchical Bayesian estimation approach to assess the single trial influence of observable physiological signals on these latent DDM parameters. Increased eye gaze dwell time specifically predicted an increased drift rate toward the fixated option, irrespective of the value of the option. In contrast, greater pupil dilation specifically predicted an increase in decision threshold during difficult decisions. These findings suggest that eye tracking and pupillometry reflect the operations of dissociated latent decision processes. |
2013 |
Christoph Scheepers; Sibylle Mohr; Martin H. Fischer; Andrew M. Roberts Listening to limericks: A pupillometry investigation of perceivers' expectancy Journal Article In: PLoS ONE, vol. 8, no. 9, pp. e74986, 2013. @article{Scheepers2013,What features of a poem make it captivating, and which cognitive mechanisms are sensitive to these features? We addressed these questions experimentally by measuring pupillary responses of 40 participants who listened to a series of Limericks. The Limericks ended with either a semantic, syntactic, rhyme or metric violation. Compared to a control condition without violations, only the rhyme violation condition induced a reliable pupillary response. An anomaly-rating study on the same stimuli showed that all violations were reliably detectable relative to the control condition, but the anomaly induced by rhyme violations was perceived as most severe. Together, our data suggest that rhyme violations in Limericks may induce an emotional response beyond mere anomaly detection. |
Jill X. O'Reilly; Urs Schuffelgen; Steven F. Cuell; Timothy E. J. Behrens; Rogier B. Mars; Matthew F. S. Rushworth Dissociable effects of surprise and model update in parietal and anterior cingulate cortex Journal Article In: Proceedings of the National Academy of Sciences, vol. 110, no. 38, pp. E3660–E3669, 2013. @article{OReilly2013,Brains use predictive models to facilitate the processing of expected stimuli or planned actions. Under a predictive model, surprising (low probability) stimuli or actions necessitate the immediate reallocation of processing resources, but they can also signal the need to update the underlying predictive model to reflect changes in the environment. Surprise and updating are often correlated in experimental paradigms but are, in fact, distinct constructs that can be formally defined as the Shannon information (IS) and Kullback-Leibler divergence (DKL) associated with an observation. In a saccadic planning task, we observed that distinct behaviors and brain regions are associated with surprise/IS and updating/DKL. Although surprise/IS was associated with behavioral reprogramming as indexed by slower reaction times, as well as with activity in the posterior parietal cortex [human lateral intraparietal area (LIP)], the anterior cingulate cortex (ACC) was specifically activated during updating of the predictive model (DKL). A second saccade-sensitive region in the inferior posterior parietal cortex (human 7a), which has connections to both LIP and ACC, was activated by surprise and modulated by updating. Pupillometry revealed a further dissociation between surprise and updating with an early positive effect of surprise and late negative effect of updating on pupil area. These results give a computational account of the roles of the ACC and two parietal saccade regions, LIP and 7a, by which their involvement in diverse tasks can be understood mechanistically. The dissociation of functional roles between regions within the reorienting/reprogramming network may also inform models of neurological phenomena, such as extinction and Balint syndrome, and neglect. |
Mariska E. Kret; Jeroen J. Stekelenburg; Karin Roelofs; Beatrice Gelder Perception of face and body expressions using electromyography, pupillometry and gaze measures Journal Article In: Frontiers in Psychology, vol. 4, pp. 28, 2013. @article{Kret2013a,Traditional emotion theories stress the importance of the face in the expression of emotions but bodily expressions are becoming increasingly important as well. In these experiments we tested the hypothesis that similar physiological responses can be evoked by observing emotional face and body signals and that the reaction to angry signals is amplified in anxious individuals. We designed three experiments in which participants categorized emotional expressions from isolated facial and bodily expressions and emotionally congruent and incongruent face-body compounds. Participants' fixations were measured and their pupil size recorded with eye-tracking equipment and their facial reactions measured with electromyography. The results support our prediction that the recognition of a facial expression is improved in the context of a matching posture and importantly, vice versa as well. From their facial expressions, it appeared that observers acted with signs of negative emotionality (increased corrugator activity) to angry and fearful facial expressions and with positive emotionality (increased zygomaticus) to happy facial expressions. What we predicted and found, was that angry and fearful cues from the face or the body, attracted more attention than happy cues. We further observed that responses evoked by angry cues were amplified in individuals with high anxiety scores. In sum, we show that people process bodily expressions of emotion in a similar fashion as facial expressions and that the congruency between the emotional signals from the face and body facilitates the recognition of the emotion. |
Kimberly S. Chiew; Todd S. Braver Temporal dynamics of motivation-cognitive control interactions revealed by high-resolution pupillometry Journal Article In: Frontiers in Psychology, vol. 4, pp. 15, 2013. @article{Chiew2013,Motivational manipulations, such as the presence of performance-contingent reward incentives, can have substantial influences on cognitive control. Previous evidence suggests that reward incentives may enhance cognitive performance specifically through increased preparatory, or proactive, control processes. The present study examined reward influences on cognitive control dynamics in the AX-Continuous Performance Task (AX-CPT), using high-resolution pupillometry. In the AX-CPT, contextual cues must be actively maintained over a delay in order to appropriately respond to ambiguous target probes. A key feature of the task is that it permits dissociable characterization of preparatory, proactive control processes (i.e., utilization of context) and reactive control processes (i.e., target-evoked interference resolution). Task performance profiles suggested that reward incentives enhanced proactive control (context utilization). Critically, pupil dilation was also increased on reward incentive trials during context maintenance periods, suggesting trial-specific shifts in proactive control, particularly when context cues indicated the need to overcome the dominant target response bias. Reward incentives had both transient (i.e., trial-by-trial) and sustained (i.e., block-based) effects on pupil dilation, which may reflect distinct underlying processes. The transient pupillary effects were present even when comparing against trials matched in task performance, suggesting a unique motivational influence of reward incentives. These results suggest that pupillometry may be a useful technique for investigating reward motivational signals and their dynamic influence on cognitive control. |
Wesley K. Burge; Lesley A. Ross; Franklin R. Amthor; William G. Mitchell; Alexander Zotov; Kristina M. Visscher Processing speed training increases the efficiency of attentional resource allocation in young adults Journal Article In: Frontiers in Human Neuroscience, vol. 7, pp. 684, 2013. @article{Burge2013,Cognitive training has been shown to improve performance on a range of tasks. However, the mechanisms underlying these improvements are still unclear. Given the wide range of transfer effects, it is likely that these effects are due to a factor common to a wide range of tasks. One such factor is a participant's efficiency in allocating limited cognitive resources. The impact of a cognitive training program, Processing Speed Training (PST), on the allocation of resources to a set of visual tasks was measured using pupillometry in 10 young adults as compared to a control group of a 10 young adults (n = 20). PST is a well-studied computerized training program that involves identifying simultaneously presented central and peripheral stimuli. As training progresses, the task becomes increasingly more difficult, by including peripheral distracting stimuli and decreasing the duration of stimulus presentation. Analysis of baseline data confirmed that pupil diameter reflected cognitive effort. After training, participants randomized to PST used fewer attentional resources to perform complex visual tasks as compared to the control group. These pupil diameter data indicated that PST appears to increase the efficiency of attentional resource allocation. Increases in cognitive efficiency have been hypothesized to underlie improvements following experience with action video games, and improved cognitive efficiency has been hypothesized to underlie the benefits of PST in older adults. These data reveal that these training schemes may share a common underlying mechanism of increasing cognitive efficiency in younger adults. |
Julie Brisson; Marc Mainville; Dominique Mailloux; Christelle Beaulieu; Josette Serres; Sylvain Sirois Pupil diameter measurement errors as a function of gaze direction in corneal reflection eyetrackers Journal Article In: Behavior Research Methods, vol. 45, no. 4, pp. 1322–1331, 2013. @article{Brisson2013,Pupil dilation is a useful, noninvasive technique for measuring the change in cognitive load. Since it is implicit and nonverbal, it is particularly useful with preverbal or nonverbal participants. In cognitive psychology, pupil dilation is most often measured by corneal reflection eye-tracking devices. The present study investigates the effect of gaze position on pupil size estimation by three common eye-tracking systems. The task consisted of a simple object pursuit situation, as a sphere rotated around the display screen. Systematic errors of pupil size estimation were found with all three systems. Implications for task-elicited pupillometry, especially for gaze-contingent studies such as object tracking or reading, are discussed. |
2011 |
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. |
2010 |
Gillian Porter; Andrea Tales; Tom Troscianko; Gordon Wilcock; Judy Haworth; Ute Leonards New insights into feature and conjunction search: I. Evidence from pupil size, eye movements and ageing Journal Article In: Cortex, vol. 46, no. 5, pp. 621–636, 2010. @article{Porter2010c,Differences in the processing mechanisms underlying visual feature and conjunction search are still under debate, one problem being a common emphasis on performance measures (speed and accuracy) which do not necessarily provide insights to the underlying processing principles. Here, eye movements and pupil dilation were used to investigate sampling strategy and processing load during performance of a conjunction and two feature-search tasks, with younger (18-27 years) and healthy older (61-83 years) age groups compared for evidence of differential age-related changes. The tasks involved equivalent processing time per item, were controlled in terms of target-distractor similarity, and did not allow perceptual grouping. Close matching of the key tasks was confirmed by patterns of fixation duration and an equal number of saccades required to find a target. Moreover, moment-to-moment pupillary dilation was indistinguishable across the tasks for both age groups, suggesting that all required the same total amount of effort or resources.Despite matching, subtle differences in eye movement patterns occurred between tasks: the conjunction task required more saccades to reach a target-absent decision and involved shorter saccade amplitudes than the feature tasks. General age-related changes were manifested in an increased number of saccades and longer fixation durations in older than younger participants. In addition, older people showed disproportionately longer and more variable fixation durations for the conjunction task specifically. These results suggest a fundamental difference between conjunction and feature search: accurate target identification in the conjunction context requires more conservative eye movement patterns, with these further adjusted in healthy ageing. The data also highlight the independence of eye movement and pupillometry measures and stress the importance of saccades and strategy for understanding the processing mechanisms driving different types of visual search. |
Paul E. Engelhardt; Fernanda Ferreira; Elena G. Patsenko Pupillometry reveals processing load during spoken language comprehension Journal Article In: Quarterly Journal of Experimental Psychology, vol. 63, no. 4, pp. 639–645, 2010. @article{Engelhardt2010,This study investigated processing effort by measuring peoples' pupil diameter as they listened to sentences containing a temporary syntactic ambiguity. In the first experiment, we manipulated prosody. The results showed that when prosodic structure conflicted with syntactic structure, pupil diameter reliably increased. In the second experiment, we manipulated both prosody and visual context. The results showed that when visual context was consistent with the correct interpretation, prosody had very little effect on processing effort. However, when visual context was inconsistent with the correct interpretation, prosody had a large effect on processing effort. The interaction between visual context and prosody shows that visual context has an effect on online processing and that it can modulate the influence of linguistic sources of information, such as prosody. Pupillometry is a sensitive measure of processing effort during spoken language comprehension. |