Direct control of fixation times in scene viewing: Evidence from analysis of the distribution of first fixation duration

Participants' eye movements were monitored in two scene viewing experiments that manipulated the task-relevance of scene stimuli and their availability for extrafoveal processing. In both experiments, participants viewed arrays containing eight scenes drawn from two categories. The arrays of scenes were either viewed freely (Free Viewing) or in a gaze-contingent viewing mode where extrafoveal preview of the scenes was restricted (No Preview). In Experiment 1a, participants memorized the scenes from one category that was designated as relevant, and in Experiment 1b, participants chose their preferred scene from within the relevant category. We examined first fixations on scenes from the relevant category compared to the irrelevant category (Experiments 1a and 1b), and those on the chosen scene compared to other scenes not chosen within the relevant category (Experiment 1b). A survival analysis was used to estimate the first discernible influence of the task-relevance on the distribution of first-fixation durations. In the free viewing condition in Experiment 1a, the influence of task relevance occurred as early as 81 ms from the start of fixation. In contrast, the corresponding value in the no preview condition was 254 ms, demonstrating the crucial role of extrafoveal processing in enabling direct control of fixation durations in scene viewing. First fixation durations were also influenced by whether or not the scene was eventually chosen (Experiment 1b), but this effect occurred later and affected fewer fixations than the effect of scene category, indicating that the time course of scene processing is an important variable mediating direct control of fixation durations.     

Eye movements and attention in reading,scene perception,and visual search

Eye movements are now widely used to investigate cognitive processes during reading, scene perception, and visual search. In this article, research on the following topics is reviewed with respect to reading: (a) the perceptual span (or span of effective vision), (b) preview benefit, (c) eye movement control, and (d) models of eye movements. Related issues with respect to eye movements during scene perception and visual search are also reviewed. It is argued that research on eye movements during reading has been somewhat advanced over research on eye movements in scene perception and visual search and that some of the paradigms developed to study reading should be more widely adopted in the study of scene perception and visual search. Research dealing with “real-world” tasks and research utilizing the visual-world paradigm are also briefly discussed.     

Influence of a psychological perspective on scene viewing and memory for scenes

In the study, 33 participants viewed photographs from either a potential homebuyer's or a burglar's perspective, or in preparation for a memory test, while their eye movements were recorded. A free recall and a picture recognition task were performed after viewing. The results showed that perspective had rapid effects, in that the second fixation after the scene onset was more likely to land on perspective-relevant than on perspective-irrelevant areas within the scene. Perspective-relevant areas also attracted longer total fixation time, more visits, and longer first-pass dwell times than did perspective-irrelevant areas. As for the effects of visual saliency, the first fixation was more likely to land on a salient than on a nonsalient area; salient areas also attracted more visits and longer total fixation time than did nonsalient areas. Recall and recognition performance reflected the eye fixation results: Both were overall higher for perspective-relevant than for perspective-irrelevant scene objects. The relatively low error rates in the recognition task suggest that participants had gained an accurate memory for scene objects. The findings suggest that the role of bottom-up versus top-down factors varies as a function of viewing task and the time-course of scene processing.     

Frequency and predictability effects in the Dundee Corpus: An eye movement analysis

Analyses carried out on a large corpus of eye movement data were used to comment on four contentious theoretical issues. The results provide no evidence that word frequency and word predictability have early interactive effects on inspection time. Contrary to some earlier studies, in these data there is little evidence that properties of a prior word generally spill over and influence current processing. In contrast, there is evidence that both the frequency and the predictability of a word in parafoveal vision influence foveal processing. In the case of predictability, the direction of the effect suggests that more predictable parafoveal words produce longer foveal fixations. Finally, there is evidence that information about word class modulates processing over a span greater than a single word. The results support the notion of distributed parallel processing.     

Cognitive control of fixation duration in visual search: The role of extrafoveal processing

Participants' eye movements were monitored in two visual search experiments that manipulated target-distractor similarity (high vs. low) as well as the availability of distractors for extrafoveal processing (Free-Viewing vs. No-Preview). The influence of the target-distractor similarity by preview manipulation on the distributions of first fixation and second fixation duration was examined by using a survival analysis technique which provided precise estimates of the timing of the first discernible influence of target-distractor similarity on fixation duration. We found a significant influence of target-distractor similarity on first fixation duration in normal visual search (Free Viewing) as early as 26–28 ms from the start of fixation. In contrast, the influence of target-distractor similarity occurred much later (199–233 ms) in the No-Preview condition. The present study also documented robust and fast acting extrafoveal and foveal preview effects. Implications for models of eye-movement control and visual search are discussed.     

Spatial frequency filtering and the direct control of fixation durations during scene viewing

The present study employed a saccade-contingent change paradigm to investigate the effect of spatial frequency filtering on fixation durations during scene viewing. Subjects viewed grayscale scenes while encoding them for a later memory test. During randomly chosen saccades, the scene was replaced with an alternate version that remained throughout the critical fixation that followed. In Experiment 1, during the critical fixation, the scene could be changed to high-pass and low-pass spatial frequency filtered versions. Under both conditions, fixation durations increased, and the low-pass condition produced a greater effect than the high-pass condition. In subsequent experiments, we manipulated the familiarity of scene information during the critical fixation by flipping the filtered scenes upside down or horizontally. Under these conditions, we observed lengthening of fixation durations but no difference between the high-pass and low-pass conditions, suggesting that the filtering effect is related to the mismatch between information extracted within the critical fixation and the ongoing scene representation in memory. We also conducted control experiments that tested the effect of changes to scene orientation (Experiment 2a) and the addition of color to a grayscale scene (Experiment 2b). Fixation distribution analysis suggested two effects on the distribution fixation durations: a fast-acting effect that was sensitive to all transsaccadic changes tested and a later effect in the tail of the distribution that was likely tied to the processing of scene information. These findings are discussed in the context of theories of oculomotor control during scene viewing.     

Fixating picture boundaries does not eliminate boundary extension: Implications for scene representation

Observers frequently remember seeing more of a scene than was shown (boundary extension). Does this reflect a lack of eye fixations to the boundary region? Single-object photographs were presented for 14–15 s each. Main objects were either whole or slightly cropped by one boundary, creating a salient marker of boundary placement. All participants expected a memory test, but only half were informed that boundary memory would be tested. Participants in both conditions made multiple fixations to the boundary region and the cropped region during study. Demonstrating the importance of these regions, test-informed participants fixated them sooner, longer, and more frequently. Boundary ratings (Experiment 1) and border adjustment tasks (Experiments 2–4) revealed boundary extension in both conditions. The error was reduced, but not eliminated, in the test-informed condition. Surprisingly, test knowledge and multiple fixations to the salient cropped region, during study and at test, were insufficient to overcome boundary extension on the cropped side. Results are discussed within a traditional visual-centric framework versus a multisource model of scene perception.     

Individual differences in spatial frequency processing in scene perception: the influence of autism-related traits

Previous research suggested that coarse (High Spatial Frequency or HSF) and fine (Low Spatial Frequency or LSF) spatial information are flexibly used at different stages of processing during scene recognition in daily life. We tried to replicate and extend these findings by presenting non-social real-life scenes either as a normal picture, solely defined by LSF or HSF information, or using hybrid images consisting of overlaid LSF and HSF scene information. These were used as (in)congruent prime stimuli, modulating the rapid detection of a normal target picture in a 2-Alternative Forced Choice (2-AFC) categorization task (manmade versus natural). Our results indicated that coarse spatial information was more effective with shorter prime presentation times and fine spatial information required a longer prime presentation to influence participant performance. Interestingly, higher scores on the Autism-Spectrum Quotient questionnaire modified the impact of HSF prime information on target identification and influenced performance when ambiguous hybrid prime information preceded the categorization task.     

A rapid effect of stimulus quality on the durations of individual fixations during reading

We developed a variant of the single fixation replacement paradigm (Yang & McConkie, 2001, 2004) in order to examine the effect of stimulus quality on fixation duration during reading. Subjects' eye movements were monitored while they read passages of text for comprehension. During critical fixations, equal changes to the luminance of the background produced either an increase (Up-Contrast) or a decrease (Down-Contrast) of the contrast of the text. The durations of critical fixations were found to be lengthened in the Down-Contrast but not the Up-Contrast condition. Ex-Gaussian modelling of the distributions of fixation durations showed that the reduction in stimulus quality lengthened the majority of fixations, and a survival analysis estimated the onset of this effect to be approximately 141 ms following fixation onset. Because the stimulus quality of the text during critical fixations could not be predicted or parafoveally previewed prior to foveation, the present effect can be attributed to an immediate effect of stimulus quality on fixation duration.     

Eye movements during scene viewing: Evidence for mixed control of fixation durations

Recent behavioral and computational research on eye movement control during scene viewing has focused on where the eyes move. However, fixations also differ in their durations, and when the eyes move may be another important indicator of perceptual and cognitive activity. Here we used a scene onset delay paradigm to investigate the degree to which individual fixation durations are under direct moment-to-moment control of the viewer’s current visual scene. During saccades just prior to critical fixations, the scene was removed from view so that when the eyes landed, no scene was present. Following a manipulated delay period, the scene was restored to view. We found that one population of fixations was under the direct control of the current scene, increasing in duration as delay increased. A second population of fixations was relatively constant across delay. The pattern of data did not change whether delay duration was random or blocked, suggesting that the effects were not under the strategic control of the viewer. The results support a mixed control model in which the durations of some fixations proceed regardless of scene presence, whereas others are under the direct moment-to-moment control of ongoing scene analysis.     

Distinguishing the effects of action relations and scene context on object perception

Objects are rarely viewed in isolation, and so how they are perceived is influenced by the context in which they are viewed and their interaction with other objects (e.g., whether objects are colocated for action). We investigated the combined effects of action relations and scene context on an object decision task. Experiment 1 investigated whether the benefit for positioning objects so that they interact is enhanced when objects are viewed within contextually congruent scenes. The results indicated that scene context influenced perception of nonaction-related objects (e.g., monitor and keyboard), but had no effect on responses to action-related objects (e.g., bottle and glass) that were processed more rapidly. In Experiment 2, we reduced the saliency of the object stimuli and found that, under these circumstances, scene context influenced responses to action-related objects. We discuss the data in terms of relatively late effects of scene processing on object perception.     

Eye movement inductions influence health behaviour: the working memory account of persuasion

Abstract

Objective: Because the working memory (WM) has a limited capacity, the cognitive reactions towards persuasive information in the WM might be disturbed by taxing it by other means, in this study, by inducing voluntary eye movements (EMi). This is expected to influence persuasion.

Methods: Participants (N?=?127) listened to an auditory persuasive message on fruit and vegetable consumption, that was either framed positively or negatively. Half of them was asked to keep following a regularly moving dot on their screen with their eyes. At pretest, cognitive self-affirmation inclination (CSAI) was assessed as individual difference to test possible moderation effects.

Results: The EMi significantly lowered the quality of the mental images that participants reported to have of the persuasive outcomes. With regard to self-reported fruit and vegetable consumption after two weeks, EMi significantly lowered consumption when CSAI was high but it significantly increased consumption when CSAI was low.

Conclusions: The results verify our earlier findings that induced EM can influence persuasion. Although it remains unclear whether the effects of EMi were caused by disturbing mental images of persuasive outcomes or self-regulative reactions to these images, or both, the WM account may provide new theoretical as well as practical angles on persuasion.     

Eye tracking research and technology: Towards objective measurement of data quality

Two methods for objectively measuring eye tracking data quality are explored. The first method works by tricking the eye tracker to detect an abrupt change in the gaze position of an artificial eye that in actuality does not move. Such a device, referred to as an artificial saccade generator, is shown to be extremely useful for measuring the temporal accuracy and precision of eye tracking systems and for validating the latency to display change in gaze contingent display paradigms. The second method involves an artificial pupil that is mounted on a computer controlled moving platform. This device is designed to be able to provide the eye tracker with motion sequences that closely resemble biological eye movements. The main advantage of using artificial motion for testing eye tracking data quality is the fact that the spatiotemporal signal is fully specified in a manner independent of the eye tracker that is being evaluated and that nearly identical motion sequence can be reproduced multiple times with great precision. The results of the present study demonstrate that the equipment described has the potential to become an important tool in the comprehensive evaluation of data quality.     

Eye movement control during reading: Effects of word frequency and orthographic familiarity

Word frequency and orthographic familiarity were independently manipulated as readers' eye movements were recorded. Word frequency influenced fixation durations and the probability of word skipping when orthographic familiarity was controlled. These results indicate that lexical processing of words can influence saccade programming (as shown by fixation durations and which words are fixated). Orthographic familiarity, but not word frequency, influenced the duration of prior fixations. These results provide evidence for orthographic, but not lexical, parafoveal-on-foveal effects. Overall, the findings have a crucial implication for models of eye movement control in reading: There must be sufficient time for lexical factors to influence saccade programming before saccade metrics and timing are finalized. The conclusions are critical for the fundamental architecture of models of eye movement control in reading -- namely, how to reconcile long saccade programming times and complex linguistic influences on saccades during reading.     

Eye movement correlates of younger and older adults' strategies for complex addition

This study examined performance measures and eye movements associated with complex arithmetic strategies in young and older adults. Participants added pairs of three-digit numbers using two different strategies, under choice and no-choice conditions. Older adults made more errors but were not significantly slower than young adults, and response times and errors showed no interaction between age and the number of carries. Older adults chose strategies less adaptively than young adults. Eye movements were consistent with use of required strategies on no-choice trials and reported strategies on choice trials. Eye movement data also suggested that young adults more successfully distinguished between strategies. Implications of these findings for understanding aging effects in complex arithmetic are discussed.     

Eye movements during the handwriting of words: Individually and within sentences

Handwriting, a complex motor process involves the coordination of both the upper limb and visual system. The gaze behavior that occurs during the handwriting process is an area that has been little studied. This study investigated the eye-movements of adults during writing and reading tasks. Eye and handwriting movements were recorded for six different words over three different tasks. The results compared reading and handwriting the same words, a between condition comparison and a comparison between the two handwriting tasks. Compared to reading, participants produced more fixations during handwriting tasks and the average fixation durations were longer. When reading fixations were found to be mostly around the center of word, whereas fixations when writing appear to be made for each letter in a written word and were located around the base of letters and flowed in a left to right direction. Between the two writing tasks more fixations were made when words were written individually compared to within sentences, yet fixation durations were no different. Correlation of the number of fixations made to kinematic variables revealed that horizontal size and road length held a strong correlation with the number of fixations made by participants.     

Word frequency in fast priming: Evidence for immediate cognitive control of eye movements during reading

Numerous studies have demonstrated effects of word frequency on eye movements during reading, but the precise timing of this influence has remained unclear. The fast priming paradigm was previously used to study influences of related versus unrelated primes on the target word. Here, we use this procedure to investigate whether the frequency of the prime word has a direct influence on eye movements during reading when the prime–target relation is not manipulated. We found that with average prime intervals of 32 ms readers made longer single fixation durations on the target word in the low than in the high frequency prime condition. Distributional analyses demonstrated that the effect of prime frequency on single fixation durations occurred very early, supporting theories of immediate cognitive control of eye movements. Finding prime frequency effects only 207 ms after visibility of the prime and for prime durations of 32 ms yields new time constraints for cognitive processes controlling eye movements during reading. Our variant of the fast priming paradigm provides a new approach to test early influences of word processing on eye movement control during reading.     

Becoming a written word: Eye movements reveal order of acquisition effects following incidental exposure to new words during silent reading

We know that from mid-childhood onwards most new words are learned implicitly via reading; however, most word learning studies have taught novel items explicitly. We examined incidental word learning during reading by focusing on the well-documented finding that words which are acquired early in life are processed more quickly than those acquired later. Novel words were embedded in meaningful sentences and were presented to adult readers early (day 1) or later (day 2) during a five-day exposure phase. At test adults read the novel words in semantically neutral sentences. Participants’ eye movements were monitored throughout exposure and test. Adults also completed a surprise memory test in which they had to match each novel word with its definition. Results showed a decrease in reading times for all novel words over exposure, and significantly longer total reading times at test for early than late novel words. Early-presented novel words were also remembered better in the offline test. Our results show that order of presentation influences processing time early in the course of acquiring a new word, consistent with partial and incremental growth in knowledge occurring as a function of an individual’s experience with each word.     

The time-course of recovery from interruption during reading: Eye movement evidence for the role of interruption lag and spatial memory

Two experiments examined how interruptions impact reading and how interruption lags and the reader's spatial memory affect the recovery from such interruptions. Participants read paragraphs of text and were interrupted unpredictably by a spoken news story while their eye movements were monitored. Time made available for consolidation prior to responding to the interruption did not aid reading resumption. However, providing readers with a visual cue that indicated the interruption location did aid task resumption substantially in Experiment 2. Taken together, the findings show that the recovery from interruptions during reading draws on spatial memory resources and can be aided by processes that support spatial memory. Practical implications are discussed.