Does conspicuity enhance distraction? Saliency and eye landing position when searching for objects

While visual saliency may sometimes capture attention, the guidance of eye movements in search is often dominated by knowledge of the target. How is the search for an object influenced by the saliency of an adjacent distractor? Participants searched for a target amongst an array of objects, with distractor saliency having an effect on response time and on the speed at which targets were found. Saliency did not predict the order in which objects in target-absent trials were fixated. The within-target landing position was distributed around a modal position close to the centre of the object. Saliency did not affect this position, the latency of the initial saccade, or the likelihood of the distractor being fixated, suggesting that saliency affects the allocation of covert attention and not just eye movements.     

The time course of attentional and oculomotor capture reveals a common cause

Eye movements are often misdirected toward a distractor when it appears abruptly, an effect known as oculomotor capture. Fundamental differences between eye movements and attention have led to questions about the relationship of oculomotor capture to the more general effect of sudden onsets on performance, known as attentional capture. This study explores that issue by examining the time course of eye movements and manual localization responses to targets in the presence of sudden-onset distractors. The results demonstrate that for both response types, the proportion of trials on which responses are erroneously directed to sudden onsets reflects the quality of information about the visual display at a given point in time. Oculomotor capture appears to be a specific instance of a more general attentional capture effect. Differences and similarities between the two types of capture can be explained by the critical idea that the quality of information about a visual display changes over time and that different response systems tend to access this information at different moments in time.     

Improved top-down control reduces oculomotor capture: The case of action video game players

Action video game players (AVGPs) have been demonstrated to outperform non-video-game players(NVGPs) on a range of cognitive tasks. Evidence to date suggests that AVGPs’ enhanced performance in attention based tasks can be accounted for by improved top-down control over the allocation of visuospatial attention. Thus,we propose that AVGPs provide a population that can be used to investigate the role of top-down factors in key models of attention. Previous work using AVGPs has indicated that they experience less interfering effects from a salient but task-irrelevant distractor in an attentional capture paradigm (Chisholm, Hickey, Theeuwes, & Kingstone,2010). Two fundamentally different bottom-up and top-down models of attention can account for this result. In the present study, we compared AVGP and NVGP performance in an oculomotor capture paradigm to address when and how top-down control modulates capture. In tracking eye movements, we acquired an explicit measurement of attention allocation and replicated the covert attention effect that AVGPs are quicker than NVGPs to attend to a target in the presence of a task-irrelevant distractor. Critically, our study reveals that this top-down gain is the result of fewer shifts of attention to the salient distractor, rather than faster disengagement after bottom-up capture has occurred. This supports the theory that top-down control can modulate the involuntary capture of attention [added].     

Age differences in the control of looking behavior: do you know where your eyes have been?

Previous research has shown that during visual search young and old adults' eye movements are equivalently influenced by the appearance of task-irrelevant abrupt onsets. The finding of age-equivalent oculomotor capture is quite surprising in light of the abundant research suggesting that older adults exhibit poorer inhibitory control than young adults on a variety of different tasks. In the present study, we examined the hypothesis that oculomotor capture is age invariant when subjects' awareness of the appearance of task-irrelevant onsets is low, but that older adults will have more difficulty than young adults in inhibiting reflexive eye movements to task-irrelevant onsets when awareness of these objects is high. Our results were consistent with the level-of-awareness hypothesis. Young and old adults showed equivalent patterns of oculomotor capture with equiluminant onsets, but older adults misdirected their eyes to bright onsets more often than young adults did.     

Influence of Task-Irrelevant Onset Distractors on the Visual Search Performance of Young and Old Adults

We examined potential age-related differences in attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. Participants were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. Either single or dual onset task-irrelevant distractors were presented simultaneously with the color change that defined the target, or one onset distractor was presented prior to and another onset distractor was presented during the participant's initial eye movement away from fixation. Young and old adults misdirected their eyes to the single and dual onset task-irrelevant distractors, on an equivalent proportion of trials, relative to control trials. However, older adults' saccade latencies and RTs were influenced to a greater extent by onsets compared to younger adults'. These data are discussed in terms of age-related differences in attentional control and oculomotor capture.     

Saccadic eye movements as indicators of cognitive function in older adults

Older adults appear to have greater difficulty ignoring distractions during day-to-day activities than younger adults. To assess these effects of age, the ability of adults aged between 50 and 80 years to ignore distracting stimuli was measured using the antisaccade and oculomotor capture tasks. In the antisaccade task, observers are instructed to look away from a visual cue, whereas in the oculomotor capture task, observers are instructed to look toward a colored singleton in the presence of a concurrent onset distractor. Index scores of the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS) were compared with capture errors, and with prosaccade errors on the antisaccade task. A higher percentage of capture errors were made on the oculomotor capture tasks by the older members of the cohort compared to the younger members. There was a weak relationship between the attention index and capture errors, but the visuospatial/constructional index was the strongest predictor of prosaccade error rate in the antisaccade task. The saccade reaction times (SRTs) of correct initial saccades in the oculomotor capture task were poorly correlated with age, and with the neurospsychological tests, but prosaccade SRTs in both tasks moderately correlated with antisaccade error rate. These results were interpreted in terms of a competitive integration (or race) model. Any variable that reduces the strength of the top-down neural signal to produce a voluntary saccade, or that increases saccade speed, will enhance the likelihood that a reflexive saccade to a stimulus with an abrupt onset will occur.     

When spiders appear suddenly: spider-phobic patients are distracted by task-irrelevant spiders

Fear is thought to facilitate the detection of threatening stimuli. Few studies have examined the effects of task-irrelevant phobic cues in search tasks that do not involve semantic categorization. In a combined reaction time and eye-tracking experiment we investigated whether peripheral visual cues capture initial attention and distract from the execution of goal-directed eye movements. Twenty-one spider-phobic patients and 21 control participants were instructed to search for a color singleton while ignoring task-irrelevant abrupt-onset distractors which contained either a small picture of a spider (phobic), a flower (non-phobic, but similar to spiders in shape), a mushroom (non-phobic, and not similar to spiders in shape), or no picture. As expected, patients' reaction times were longer on trials with spider distractors. However, eye movements revealed that this was not due to attentional capture by spider distractors; patients more often fixated on all distractors with pictures, but their reaction times were delayed by longer fixation durations on spider distractors. These data do not support automatic capture of attention by phobic cues but suggest that phobic patients fail to disengage attention from spiders.     

Oculomotor evidence of sequence learning on the serial reaction time task

Manual and oculomotor measures of sequence learning were examined on the serial reaction time (SRT) task Participants were assigned into four groups differing on response modality (manual, oculomotor) and trial type (sequence, pseudorandom). The pattern of manual RTs replicated previous studies. Frequency of anticipatory eye movements followed similar patterns as RTs. Participants made many anticipations, even in pseudorandom blocks, and frequency of anticipations did not depend on presence of concurrent manual responses. Excluding participants with explicit awareness did not change results. Anticipations were negatively related to RTs in both incidental and intentional learning. Anticipations were positively related to sequence recall in intentional, but not incidental, learning. Results suggest that (1) anticipatory eye movements reflected sequence learning and (2) participants made overt and covert shifts of visuospatial attention to likely stimulus locations prior to stimulus onset, whether or not they made manual responses and whether or not there was a sequence.     

Conscious error perception: The impact of response interference from a secondary task

An erroneous response is not always accompanied by the conscious perception of the error being made. We examined whether increased response interference on a manual task improved the conscious perception of erroneous eye movements on a concurrent oculomotor task. In the first experiment, we examined whether a correlate of response interference, increased task difficulty alone, could improve perception of errors. We found no effect of task difficulty on self-monitoring. Results from a second experiment suggested that participants’ ability to monitor their eye movements improved with increased response interference, but post hoc analyses indicated that this was due to a decrease in corrective behaviors. Experiment 3 required participants to report directly on whether they had made an eye movement error, and we found that response interference perturbed, rather than improved, participants’ ability to report on their errors. Together, these findings contribute to models of error monitoring, revealing little support for the view that general increases in response interference or task difficulty are signals that contribute to the conscious detection of errors.     

Knowing and avoiding: The influence of distractor awareness on oculomotor capture

Kramer, Hahn, Irwin, and Theeuwes (2000) reported that the interfering effect of distractors is reduced when participants are aware of the to-be-ignored information. In contrast, recent evidence indicates that distractor interference increases when individuals are aware of the distractors. In the present investigation, we directly assessed the influence of distractor awareness on oculomotor capture, with the hope of resolving this contradiction in the literature and gaining further insight into the influence of awareness on attention. Participants completed a traditional oculomotor capture task. They were not informed of the presence of the distracting information (unaware condition), were informed of distractors (aware condition), or were informed of distractor information and told to avoid attending to it (avoid condition). Being aware of the distractors yielded a performance benefit, relative to the unaware condition; however, this benefit was eliminated when participants were told to actively avoid distraction. This pattern of results reconciles past contradictions in the literature and suggests an inverted-U function of awareness in distractor performance. Too little or too much emphasis yields a performance decrement, but an intermediate level of emphasis provides a performance benefit.     

Attentional capture and aging: implications for visual search performance and oculomotor control

Two studies examined potential age-related differences in attentional capture. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside it. On half the trials, a new stimulus (i.e., a sudden onset) appeared simultaneously with the presentation of the color singleton target. The onset was always a task-irrelevant distractor. Response times were lengthened, for both young and old adults, whenever an onset distractor appeared, despite the fact that subjects reported being unaware of the appearance of the abrupt onset. Eye scan strategies were also disrupted by the appearance of the onset distractors. On about 40% of the trials on which an onset appeared, subjects made an eye movement to the task-irrelevant onset before moving their eyes to the target. Fixations close to the onset were brief, suggesting parallel programming of a reflexive eye movement to the onset and goal-directed eye movement to the target. Results are discussed in terms of age-related sparing of the attentional and oculomotor processes that underlie attentional capture.     

Value-driven attentional and oculomotor capture during goal-directed, unconstrained viewing

Covert shifts of attention precede and direct overt eye movements to stimuli that are task relevant or physically salient. A growing body of evidence suggests that the learned value of perceptual stimuli strongly influences their attentional priority. For example, previously rewarded but otherwise irrelevant and inconspicuous stimuli capture covert attention involuntarily. It is unknown, however, whether stimuli also draw eye movements involuntarily as a consequence of their reward history. Here, we show that previously rewarded but currently task-irrelevant stimuli capture both attention and the eyes. Value-driven oculomotor capture was observed during unconstrained viewing, when neither eye movements nor fixations were required, and was strongly related to individual differences in visual working memory capacity. The appearance of a reward-associated stimulus came to evoke pupil dilation over the course of training, which provides physiological evidence that the stimuli that elicit value-driven capture come to serve as reward-predictive cues. These findings reveal a close coupling of value-driven attentional capture and eye movements that has broad implications for theories of attention and reward learning.     

Age-related effects of attentional and oculomotor capture by onsets and color singletons as a function of experience

The present experiment examined the degree to which experience with different stimulus characteristics affects attentional capture, particularly as related to aging. Participants were presented with onset target/color singleton distractor or color singleton target/onset distractor pairs across three experimental sessions. The target/distractor pairs were reversed in the second session such that the target in the first session became the distractor in the second and third sessions. For both young and old adults previous experience with color as a target defining feature influenced oculomotor capture with task-irrelevant color distractors. Experience with sudden onsets had the same effect for younger and older adults, although capture effects were substantially larger for onset than for color distractors. Experience-based capture effects diminished relatively rapidly after target and distractor-defining properties were reversed. The results are discussed in terms of top-down and stimulus-driven effects on age-related differences in attentional control.     

Attentional and oculomotor capture with static singletons

Previous research has shown that in visual search static singletons have the ability to capture attention (Theeuwes, 1991a, 1992). The present study investigated whether these singletons also have the ability to capture the eyes. Participants had to make an eye movement and respond manually to a shape singleton while a color singleton was present. When participants searched for a unique shape while a unique color singleton was present there was strong attentional and oculomotor capture (Experiment 1). However, when participants searched for a specific-shape singleton (a green circle) when a specific-color singleton (a red element) had to be ignored, there was attentional capture but no oculomotor capture (Experiment 2). The results suggest that an attentional set for a specific feature value defining both the target and the distractor (as in Experiment 2) allows such a fast disengagement of attention from the location of the distractor that a saccade execution to that location is prevented.     

Visuospatial perceptual sequence learning and eye movements

We examined perceptual sequence learning by means of an adapted serial reaction time task in which eye movements were unnecessary for performing the sequence learning task. Participants had to respond to the identity of a target letter pair ("OX" or "XO") appearing in one of four locations. On the other locations, similar distractor letter pairs ("QY" or "YQ") were shown. While target identity changed randomly, target location was structured according to a deterministic sequence. To render eye movements superfluous, (1) stimulus letter pairs appeared around a fixation cross with a visual angle of 0.63°, which means that they appeared within the foveal visual area and (2) the letter pairs were presented for only 100 ms, a period too short to allow proper eye movements. Reliable sequence knowledge was acquired under these conditions, as responses were both slower and less accurate when the trained sequence was replaced by an untrained sequence. These results support the notion that perceptual sequence learning can be based on shifts of attention without overt oculomotor movements.     

Response inhibition in motor and oculomotor conflict tasks: Different mechanisms,different dynamics?

Previous research has shown that the appearance of task-irrelevant abrupt onsets influences saccadic eye movements during visual search and may slow down manual reactions to target stimuli. Analysis of reaction time distributions in the present study offers evidence suggesting that top-down inhibition processes actively suppress oculomotor or motor responses elicited by a salient distractor, in order to resolve the conflict that arises when reflex-like and deliberate responses are in opposition. Twenty-six participants carried out a variation of the oculomotor capture task. They were instructed to respond with either a saccade toward or with a button press at the side of the hemifield in which a target color singleton appeared. A distractor stimulus could appear either in the same or in the opposite hemifield. Delta plots revealed competition between reflex-like and deliberate response activation, and highlighted selective inhibition of automatic responses: While participants generally responded more slowly in incongruent compared to congruent situations, this effect diminished and even reversed in the slowest speed quantiles. These effects were present in both the oculomotor and motor response-mode conditions.     

Overt and covert object-based attention

To examine the role of perceptual object representations in the control of eye movements and attention, a pair of experiments adapted the object-cuing paradigm of Egly, Driver, and Rafal (1994) to require eye movements. Displays were pairs of adjacent rectangles, each containing two characters. Observers were asked to make a speeded judgment of a target character’s orientation, and a cue was provided prior to target/distractor onset to indicate the target’s likely location. Gaze-contingent presentation of target and distractors was used to demand overt scanning of displays. Eye movements during task performance evinced two forms of object-based effects. First, saccades following fixation on an invalidly cued item were more likely to be made within the cued rectangle than between rectangles. Second, saccades within the cued rectangle were preceded by shorter dwell times than saccades between rectangles. Extrafoveal processing of stimuli within the cued rectangle, however, was not facilitated, suggesting that covert attention was not allocated more densely within the cued than within the uncued object.     

Modulation of oculomotor capture by abrupt onsets during attentionally demanding visual search

The influence of abrupt onsets on attentionally demanding visual search (i.e., search for a letter target among heterogeneous letter distractors), as indexed by performance and eye movement measures, was investigated in a series of studies. In Experiments 1 and 2 we examined whether onsets would capture the eyes when the appearance of an onset predicted neither the location nor the identity of the target. Subjects did direct their eyes to the abrupt onsets on a disproportionate number of trials in these studies. Interestingly, however, onset capture was modulated by subjects' scan strategies. Furthermore, onsets captured the eyes less frequently than would have been predicted by paradigms showing attentional capture when no eye movements are required. Experiment 3 examined the question of whether onsets would capture the eyes in a situation in which they never served as the target. Capture was observed in this study. However, the magnitude of capture effects was substantially diminished as compared to previous behavioural studies in which the onset had a chance probability of serving as the target. These data are discussed in terms of the influence of top-down constraints on stimulus-driven attentional and oculomotor capture by abrupt onset stimuli.     

Development of attentional and oculomotor control

The present study was conducted to examine the development of attentional and oculomotor control. More specifically, the authors were interested in the development of the ability to inhibit an incorrect but prepotent response to a salient distractor. Participants, who ranged in age from 8 to 25 years, performed 3 different eye movement tasks: a prosaccade, an antisaccade, and an oculomotor capture task. The time required to initiate a saccade decreased with age across all 3 tasks. Consistent with previous reports, accuracy was relatively age invariant in the prosaccade task. Performance improved with age, asymptoting at 16 years in the antisaccade task. It is interesting to note that despite the superficial similarity of the antisaccade and oculomotor capture tasks, performance was relatively age invariant in the latter. These results are discussed in terms of developmental differences in the interaction of goal-directed and stimulus-driven processes in the control of attention and action.