Collisions and attention Journal Article
In: ACM Transactions on Applied Perception, vol. 2, no. 3, pp. 309–321, 2005.
Attention is an important factor in the perception of static and dynamic scenes, which should, therefore, be taken into account when creating graphical images and animation. Recently, researchers have recognized this fact and have been investigating how the focus of attention can be measured, predicted, and exploited in graphical systems. In this article, we explore some preliminary strategies for developing an automatic means of predicting and exploiting attention in the processing of collisions and other dynamic events. Recent work on the perception of causality has shown that attention can change the way in which a dynamic scene consisting of collision events is perceived. We describe a series of experiments designed to determine the source of biases in the perception of anomalous collision dynamics and, in particular, whether attention plays a role. Using an eyetracker, eye-movements were recorded while participants viewed animations of simple causal launching events in 3D involving two colliding spheres. Results indicated that there was indeed a definite pattern to the allocation of attention based on the nature of the event, which is promising for the goal of developing a predictive metric. As a follow-up, a paper-based experiment was carried out in which participants were asked to sketch the predicted post-collision trajectories of the same two spheres printed on paper. These experiments demonstrated that attention alone was not sufficient in determining performance, but rather the nature of the dynamic event itself also played a role.
Sequential Processing in Comprehension of Hierarchical Graphs Journal Article
In: Applied Cognitive Psychology, vol. 18, pp. 467–480, 2004.
Hierarchical graphs represent the relationships between non-numerical entities or concepts (like computer file systems, family trees, etc). Graph nodes represent the concepts and interconnecting lines represent the relationships. We recorded participants' eye movements while viewing such graphs to test two possible models of graph comprehension. Graph readers had to answer interpretive questions, which required comparisons between two graph nodes. One model postulates a search and a combined search-reasoning stage of graph comprehension (two-stage model), whereas the second model predicts three stages, two stages devoted to the search of the relevant graph nodes and a separate reasoning stage. A detailed analysis of the eye movement data provided clear support for the three-stage model. This is in line with recent studies, which suggest that participants serialize problem solving tasks in order to minimize the overall processing load.
Jason S. McCarley; Arthur F. Kramer; Christopher D. Wickens; Eric D. Vidoni; Walter R. Boot
Visual skills in airport security inspection Journal Article
In: Psychological Science, vol. 15, no. 5, pp. 302–306, 2004.
An experiment examined visual performance in a simulated luggage-screening task. Observers participated in five sessions of a task requiring them to search for knives hidden in x-ray images of cluttered bags. Sensitivity and response times improved reliably as a result of practice. Eye movement data revealed that sensitivity increases were produced entirely by changes in observers' ability to recognize target objects, and not by changes in the effectiveness of visual scanning. Moreover, recognition skills were in part stimulus-specific, such that performance was degraded by the introduction of unfamiliar target objects. Implications for screener training are discussed.
David Crundall; Claire Shenton; Geoffrey Underwood
Eye movements during intentional car following Journal Article
In: Perception, vol. 33, no. 8, pp. 975–986, 2004.
Does intentional car following capture visual attention to the extent that driving may be impaired? We tested fifteen participants on a rudimentary driving simulator. Participants were either instructed to follow a vehicle ahead through a simulated version of London, or were given verbal instructions on where to turn during the route. The presence or absence of pedestrians, and the simulated time of the drive (day or night) were varied across the trials. Eye movements were recorded along with behavioural measures including give-way violations, give-way accidents, and kerb impacts. The results revealed that intentional car following reduced the spread of search and increased fixation durations, with a dramatic increase in the time spent processing the vehicle ahead (controlled for exposure). The effects were most pronounced during nighttime drives. During the car-following trials participants were also less aware of pedestrians, produced more give-way violations, and were involved in more give-way accidents. The results draw attention to the problems encountered during car following, and we relate this to the cognitive demands placed on drivers, especially police drivers who often engage in intentional car following and pursuits.
Dimitris Agrafiotis; Nishan Canagarajah; David R. Bull; Matthew Dye
Perceptually optimised sign language video coding based on eye tracking analysis Journal Article
In: Electronics Letters, vol. 39, pp. 1–2, 2003.
A perceptually optimised approach to sign language video coding is presented. The proposed approach is based on the results (included) of an eye tracking study in the visual attention of sign language viewers. Results show reductions in bit rate of over 30% with very good subjective quality.
David Crundall; Peter Chapman; Nicola Phelps; Geoffrey Underwood
Eye movements and hazard perception in police pursuit and emergency response driving Journal Article
In: Journal of Experimental Psychology: Applied, vol. 9, no. 3, pp. 163–174, 2003.
How do police cope with the visual demands placed on them during pursuit driving? This study compared the hazard ratings, eye movements, and physiological responses of police drivers with novice and with age-matched control drivers while viewing video clips of driving taken from police vehicles. The clips included pursuits, emergency responses, and control drives. Although police drivers did not report more hazards than the other participants reported, they had an increased frequency of electrodermal responses while viewing dangerous clips and a greater visual sampling rate and spread of search. However, despite an overall police advantage in oculomotor and physiological measures, all drivers had a reduced spread of search in nighttime pursuits because of the focusing of overt attention.
Elizabeth Gilman; Geoffrey Underwood
Restricting the field of view to investigate the perceptual spans of pianists Journal Article
In: Visual Cognition, vol. 10, no. 2, pp. 201–232, 2003.
An experiment is reported, which was designed to determine how the perceptual span of pianists varies with developing skill and cognitive load. Eye-movements were recorded as musical phrases were presented through a gaze-contingent window, which contained one beat, two beats, or four beats. In a control condition, the music was presented without a window. The pianists were required to perform three tasks of varying cognitive load: An error-detection task (low load); a sight- reading task (medium load); and a transposition task (high load). Measures taken comprised fixation duration, fixation frequency, saccade length, fixation locations, performance duration, note duration, position of first error, number of errors, and eye±hand span. The results indicate that good and poor sight-readers do not differ in terms of perceptual span. However, good sight-readers were found to have larger eye±hand spans. Furthermore, the results show that increasing cognitive load decreases eye±hand span, but has little effect on perceptual span.
Tomas Lindberg; Risto Näsänen
The effect of icon spacing and size on the speed of icon processing in the human visual system Journal Article
In: Displays, vol. 24, no. 3, pp. 111–120, 2003.
Alphanumeric and graphical information needs to be presented in such a way that its perception is accurate, fast and as effortless as possible. This study investigated the effects of spacing and size of individual interface elements on their perception. Experiment 1 investigated the effect of icon spacing on the speed of visual search for a target icon and determined the perceptual span for icons, that is, the number of icons that can be processed by one eye fixation. Experiment 2 studied the effect of size, and experiment 3 the subjective preferences for levels of icon spacing. The results of experiment 1 showed that spacing does not have an effect on search times. On average the perceptual span for icons was found to be 25 arranged in a 5 × 5 array. The size of the interface elements, on the other hand, was found to have a great effect. Icons smaller than 0.7° resulted in significantly raised search times. Experiment 3 revealed that an inter-element spacing of one icon is to be preferred and a spacing of zero icons is to be avoided.
Risto Näsänen; Helena Ojanpää
Effect of image contrast and sharpness on visual search for computer icons Journal Article
In: Displays, vol. 24, pp. 137–144, 2003.
The purpose of the study was to determine the effect of image blur and contrast on the speed of visual search for user interface icons and investigate how the effect is reflected in eye movement parameters. The task of the observer was to search for a target icon from among a rectangular array of distracter icons. A staircase algorithm was used to determine the stimulus presentation time, threshold search time, for which the probability of correct responses was 0.79. Simultaneously, eye-movements were recorded with a video eye-tracker with a sampling rate of 250 Hz. Image sharpness was varied by filtering the stimulus images with a Gaussian low-pass filter. The results showed that with increasing contrast or sharpness search time, number of fixations per search, and fixation duration first decreased, and then became constant at medium levels of contrast or sharpness. These effects were somewhat more pronounced for contrast than for sharpness. Saccade amplitudes were not affected by contrast or sharpness. The results suggest that the perception of user interface icons is quite resistant to small or moderate deterioration of image quality.
Helena Ojanpää; Risto Näsänen
Effects of luminance and colour contrast on the search of information on display devices Journal Article
In: Displays, vol. 24, no. 4-5, pp. 167–178, 2003.
For black-and-white alphanumeric information, the speed of visual perception decreases with decreasing contrast. We investigated the effect of luminance contrast on the speed of visual search and reading when characters and background differed also with respect to colour. The luminance contrast between background and characters was varied, while colour contrast was held nearly constant. Stimuli with moderate (green/grey) or high colour contrast (green/red or yellow/blue), and three character sizes (0.17, 0.37, and 1.26deg) were used. Eye movements were recorded during the visual search task. We found that the visual search times, number of eye fixations, and mean fixation durations increased strongly with decreasing luminance contrast despite the presence of colour contrast. The effects were largest for small characters (0.17deg), but occurred also for medium (0.37deg), and in some cases for large (1.26deg) characters. Similarly, reading rates decreased with decreasing luminance contrast. Thus, moderate or even high colour contrast does not guarantee quick visual perception, if the luminance contrast between characters and background is small. This is probably due to the fact that visual acuity (the ability to see small details) is considerably lower for pure colour information than for luminance information. Therefore, in user interfaces, good visibility of alphanumeric information requires clear luminance (brightness) difference between foreground and background.
Tanja R. M. Coeckelbergh
The effect of visual field defects on driving performance Journal Article
In: Archives of Ophthalmology, vol. 120, no. 11, pp. 1509–1516, 2002.
Objectives: To investigate the effect of visual field de-fects on driving performance, and to predict practical fit-ness to drive. Methods: The driving performance of 87 subjects with visual field defects due to ocular abnormalities was as-sessed on a driving simulator and during an on-road driv-ing test. Outcome Measures: The final score on the on-road driving test and simulator indexes, such as driving speed, viewing behavior, lateral position, time-headway, and time to collision. Results: Subjects with visual field defects showed dif-ferential performance on measures of driving speed, steer-ing stability, lateral position, time to collision, and time-headway. Effective compensation consisted of reduced driving speed in cases of central visual field defects and increased scanning in cases of peripheral visual field de-fects. The sensitivity and specificity of models based on vision, visual attention, and compensatory viewing effi-ciency were increased when the distance at which the sub-ject started to scan was taken into account. Conclusions: Subjects with visual field defects demon-strated differential performance on several driving simu-lator indexes. Driving examiners considered reduced speed and increased scanning to be valid compensation for cen-tral and peripheral visual field defects, respectively. Pre-dicting practical fitness to drive was improved by taking driving simulator indexes into account.
Tanja R. M. Coeckelbergh; Frans W. Cornelissen; Wiebo H. Brouwer; Aart C. Kooijman
The effect of visual field defects on eye movements and practical fitness to drive Journal Article
In: Vision Research, vol. 42, no. 5, pp. 669–677, 2002.
Eye movements of subjects with visual field defects due to ocular pathology were monitored while performing a dot counting task and a visual search task. Subjects with peripheral field defects required more fixations, longer search times, made more errors, and had shorter fixation durations than control subjects. Subjects with central field defects performed less well than control subjects although no specific impairment could be pinpointed. In both groups a monotonous relationship was observed between the visual field impairment and eye movement parameters. The use of eye movement parameters to predict viewing behavior in a complex task (e.g. driving) was limited.
Boris M. Velichkovsky; Sascha M. Dornhoefer; Mathias Kopf; Jens R. Helmert; Markus Joos
Change detection and occlusion modes in road-traffic scenarios Journal Article
In: Transportation Research Part F: Traffic Psychology and Behaviour, vol. 5, no. 2, pp. 99–109, 2002.
Change blindness phenomena are widely known in cognitive science, but their relation to driving is not quite clear. We report a study where subjects viewed colour video stills of natural traffic while eye movements were recorded. A change could occur randomly in three different occlusion modes-blinks, blanks and saccades-or during a fixation (as control condition). These changes could be either relevant or irrelevant with respect to the traffic safety. We used deletions as well as insertions of objects. All occlusion modes were equivalent concerning detection rate and reaction time, deviating from the control condition only. The detection of relevant changes was both more likely and faster than that of irrelevant ones, particularly for relevant insertions, which approached the base line level. Even in this case, it took about 180 ms longer to react to changes when they occurred during a saccade, blink or blank. In a second study, relevant insertions and the blank occlusion were used in a driving simulator environment. We found a surprising effect in the dynamic setting: an advantage in change detection rate and time with blanks compared to the control condition. Change detection was also good during blinks, but not in saccades. Possible explanation of these effects and their practical implications are discussed.
Risto Näsänen; Jan Karlsson; Helena Ojanpää
Display quality and the speed of visual letter search Journal Article
In: Displays, vol. 22, no. 4, pp. 107–113, 2001.
Previously it has been suggested that visual search tasks can be used to evaluate the perceptual quality of display devices with respect to their ability to convey alphanumeric information. The purpose of the present study was to examine how character size and contrast used in a visual search test affects its sensitivity to differences in the quality of display devices. The task of the observer was to search for, and identify, an uppercase letter from a rectangular array of characters in which the other items were numerals. Threshold search time, that is, the duration of stimulus presentation required for search that is successful with a given probability, was determined by using a multiple-alternative staircase method. Eye movements were recorded simultaneously by using a fast video eye tracker. Threshold search times were measured as a function of character size at two contrast levels using a CRT and an LCD display. For all experimental conditions, threshold search time decreased with increasing letter size. This was accompanied with a decrease in the number of eye fixations per search as well as a decrease of fixation duration. At high contrast (CMichelson≈ 1), no statistically significant difference was found between the two displays. However, at the lower contrast used (CMichelson≈ 0.2) and at small character sizes, threshold search times for the CRT display were clearly longer and the number of fixations per search was higher than for the LCD display. In conclusion, visual letter search is a more sensitive method for display evaluation at small contrasts and with small character sizes.
Risto Näsänen; Helena Ojanpää; Ilpo Kojo
Effect of stimulus contrast on performance and eye movements in visual search Journal Article
In: Vision Research, vol. 41, no. 14, pp. 1817–1824, 2001.
According to the visual span control hypothesis, eye movements are controlled in relation to the size of visual span. In reading, the decrease of contrast reduces visual span, saccade sizes, and reading speed. The purpose of the present study is to determine how stimulus contrast affects the speed of two-dimensional visual search and how changes in eye movements and visual span could explain changes in performance. The task of the observer was to search for, and identify, an uppercase letter from a rectangular array of characters in which the other items were numerals. Threshold search time, i.e. the duration of stimulus presentation required for search that is successful with a given probability, was determined by using a multiple-alternative staircase method. Eye movements were recorded simultaneously by using a video eye tracker. Four different set sizes (the sizes of stimulus array) (3 × 3-10 × 10), and five different contrasts (0.0186 - 0.412) were used. At all set sizes, threshold search time decreased with increasing contrast. Also the average number of fixations per search decreased with increasing contrast. At the smallest set size (3 × 3), only one fixation was needed except at the lowest contrast. Average fixation duration decreased and saccade amplitudes increased slightly with increasing contrast. The reduction of the number of fixations with increasing contrast suggests that visual span, i.e. the area from which information can be collected at one fixation, increases with increasing contrast. The reduction of the number of fixations together with reduced fixation duration result in reduced search times when contrast increases.
Keith Rayner; Caren M. Rotello; Andrew J. Stewart; Jessica Keir; Susan A. Duffy
Integrating text and pictorial information: Eye movements when looking at print advertisements Journal Article
In: Journal of Experimental Psychology: Applied, vol. 7, no. 3, pp. 219–226, 2001.
Viewers looked at print advertisements as their eye movements were recorded. Half of them were told to pay special attention to car ads, and the other half were told to pay special attention to skin-care ads. Viewers tended to spend more time looking at the text than the picture part of the ad, though they did spend more time looking at the type of ad they were instructed to pay attention to. Fixation durations and saccade lengths were both longer on the picture part of the ad than the text, but more fixations were made on the text regions. Viewers did not alternate fixations between the text and picture part of the ad, but they tended to read the large print, then the smaller print, and then they looked at the picture (although some viewers did an initial cursory scan of the picture). Implications for (a) how viewers integrate pictorial and textual information and (b) applied research and advertisement development are discussed.
Eyal M. Reingold; Neil Charness; Marc Pomplun; Dave M. Stampe
Visual span in expert chess players: Evidence from eye movements Journal Article
In: Psychological Science, vol. 12, no. 1, pp. 48–55, 2001.
The reported research extends classic findings that after briefly viewing structured, but not random, chess positions, chess masters reproduce these positions much more accurately than lessskilled players. Using a combination of the gaze-contingent window paradigm and the change blindness flicker paradigm, we documented dramatically larger visual spans for experts while processing structured, but not random, chess positions. In addition, in a checkdetection task, a minimized 3 × 3 chessboard containing a King and potentially checking pieces was displayed. In this task, experts made fewer fixations per trial than less-skilled players, and had a greater proportion of fixations between individual pieces, rather than on pieces. Our results provide strong evidence for a perceptual encoding advantage for experts attributable to chess experience, rather than to a general perceptual or memory superiority.