Offset transients modulate attentional capture by sudden onsets

Do New Objects Capture Attention?

The visual system relies on several heuristics to direct attention to important locations and objects. One of these mechanisms directs attention to sudden changes in the environment. Although a substantial body of research suggests that this capture of attention occurs only for the abrupt appearance of a new perceptual object, more recent evidence shows that some luminance-based transients (e.g., motion and looming) and some types of brightness change also capture attention. These findings show that new objects are not necessary for attention capture. The present study tested whether they are even sufficient. That is, does a new object attract attention because the visual system is sensitive to new objects or because it is sensitive to the transients that new objects create? In two experiments using a visual search task, new objects did not capture attention unless they created a strong local luminance transient.

Attentional capture by motion onsets is modulated by perceptual load

The onset of motion captures attention during visual search even if the motion is not task relevant, which suggests that motion onsets capture attention in a stimulus-driven manner. However, we have recently shown that stimulus-driven attentional capture by abruptly appearing objects is attenuated under conditions of high perceptual load. In the present study, we examined the influence of perceptual load on attentional capture by another type of dynamic stimulus: the onset of motion. Participants searched for a target letter through briefly presented low- and high-load displays. On each trial, two irrelevant flankers also appeared, one with a motion onset and one that was static. Flankers defined by a motion onset captured attention in the low-load but not in the high-load displays. This modulation of capture in high-load displays was not the result of overall lengthening of reaction times (RTs) in this condition, since search for a single low-contrast target lengthened RTs but did not influence capture. These results, together with those of previous studies, suggest that perceptual load can modulate attentional capture by dynamic stimuli.

Attentional capture by object appearance and disappearance

In two experiments we examined whether the appearance of a new object has attentional priority over disappearance. Previous failures to show differences are possibly due to onsets and offsets always being presented as a sole visual transient. Rather than presenting each alone, we presented onset and offset singletons simultaneously with a display-wide luminance transient in order to force each to compete with other visual events. Results from Experiment 1 showed that targets associated with onsets accrued a reaction time benefit whilst targets associated with offsets did not. Experiment 2 showed that onsets attracted attention even when observers were attentionally set to look for offset. By contrast, offsets needed a relevant attentional set in order to attract attention. We argue that the appearance of an object has attentional priority over disappearance.

Displaywide visual features associated with a search display’s appearance can mediate attentional capture

Whether or not the capture of visual attention is driven solely by the salience of an attention-capturing stimulus or mediated by top-down control has been a point of contention since Folk, Remington, and Johnston (1992) introduced their contingent involuntary orienting hypothesis, which states that the capture of attention by a salient stimulus depends on its relevance to a feature distinguishing the target from nontargets. Gibson and Kelsey (1998) extended Folk et al.'s (1992) hypothesis by demonstrating that features associated with the appearance of the target display also mediate capture. Although similar to Folk et al. (1992), Gibson and Kelsey's displaywide contingent orienting hypothesis makes it difficult to demonstrate stimulus-driven capture, because an observer must always use some perceptible feature as a signal of the target display's appearance; hence, such features could always be mediating capture. The present article reviews and applies the logic of Gibson and Kelsey's and Folk et al.'s (1992) hypotheses to experiments from the attentional capture literature, and assesses whether previously reported capture effects were mediated by top-down attentional control. It concludes that these capture effects were not stimulus-driven.

Do “mudsplashes” induce tactile change blindness?

The phenomenon of change blindness (the surprising inability of people to correctly perceive changes between consecutively presented displays), primarily reported in vision, has recently been shown to occur for positional changes presented in tactile displays as well. Here, we studied people's ability to detect changes in the number of tactile stimuli in successively presented displays composed of one to three stimuli distributed over the body surface. In Experiment 1, a tactile mask consisting of the simultaneous activation of all seven possible tactile stimulators was sometimes presented between the two to-be-discriminated tactile displays. In Experiment 2, a "mudsplash" paradigm was used, with a brief irrelevant tactile distractor presented at the moment of change of the tactile display. Change blindness was demonstrated in both experiments, thus showing that the failure to detect tactile change is not necessarily related to (1) the physical disruption between consecutive events, (2) the effect of masking covering the location of the change, or (3) the erasure or resetting of the information contained within an internal representation of the tactile display. These results are interpreted in terms of a limitation in the number of spatial locations/events that can be consciously accessed at any one time. This limitation appears to constrain change-detection performance, no matter the sensory modality in which the stimuli are presented.

When visual transients impair tactile change detection: A novel case of crossmodal change blindness?

The inability of people to detect changes between consecutively presented visual displays, when separated by a blank screen or distractor, is known as "change blindness". This phenomenon has recently been reported to occur within the auditory and tactile modalities as well. To date, however, only distractors presented within the same sensory modality as the change have been demonstrated to produce change blindness. In the present experiment, we studied whether tactile change blindness might also be elicited by the presentation of a visual mask. Participants made same versus different judgments regarding two successively presented displays composed of two to three vibrotactile stimuli. While change detection performance was near-perfect when the two displays were presented one directly after the other, participants failed to detect many of the changes between the tactile displays when they were separated by an empty temporal interval. Critically, performance deteriorated still further when the presentation of a local (i.e., a mudsplash) or global visual transient coincided with the onset of the second tactile pattern. Analysis of the results using signal detection theory revealed that this crossmodal effect reflected a genuine perceptual impairment.

The dynamic events that capture visual attention: A reply to Abrams and Christ (2005)

We recently demonstrated that, contrary to previous findings, some types of irrelevant motion are capable of capturing our attention (Franconeri & Simons, 2003). Strikingly, whereas sitmulated looming (a dynamic increase in object size) captured attention, simulated receding (a decrease in object size) did not. Abrams and Christ (2003, 2005) have provided a different interpretation of this evidence, arguing that in each case attention was captured by the onset of motion rather than by motion per se. They argued that the only published finding inconsistent with their motion onset account is our evidence that simulated receding motion failed to capture attention. Abrams and Christ (2005) presented a receding object stereoscopically and found that it did capture attention, leading them to conclude that the motion onset account explains existing data more parsimoniously than our account does. Our reply has three parts. First, we argue that evidence of capture by receding motion is interesting but irrelevant to the debate over whether capture by motion requires a motion onset. Second, we show that the original empirical evidence in support of the motion onset claim (Abrams & Christ, 2003) put the motion-only condition at a critical disadvantage. We present a new experiment that demonstrates strong capture by motion in the absence of a motion onset, showing that motion onsets are not necessary for attention capture by dynamic events. Finally, we outline what is known about the set of dynamic events that capture attention.

Oculomotor consequences of abrupt object onsets and offsets: onsets dominate oculomotor capture

Previous research has shown that the appearance of an object (onset) and the disappearance of an object (offset) have the ability to influence the allocation of covert attention. To determine whether both onsets and offsets have the ability to influence eye movements, a series of experiments was conducted in which participants had to make goal-directed eye movements to a color singleton target in the presence of an irrelevant onset/offset. In accord with previous research, onsets had the ability to capture the eyes. The offset of an object demonstrated little or no ability to interrupt goal-directed eye movements to the target. Two experiments in which the effects of onsets and offsets on covert attention were examined suggest that offsets do not capture the eyes, because they have a lesser ability to capture covert attention than do onsets. A number of other studies that have shown strong effects of offsets on attention have used offsets that were uncorrelated with target position (i.e., nonpredictive), whereas we used onsets and offsets that never served as targets (i.e., antipredictive). The present results are consistent with a new-object theory of attentional capture in which onsets receive attentional priority over other types of changes in the visual environment.

Detecting transient changes in dynamic displays: the more you look, the less you see

OBJECTIVE

Two experiments examined the detectability of transient changes in cluttered and dynamic displays and optimal scan strategies for performance.

BACKGROUND

Research has demonstrated that onset changes are prioritized by the attention system and onsets are often used to signal important display changes. However, research has mostly used uncluttered, static displays and has largely ignored the role of scan strategy.

METHOD

We had participants monitor a cluttered and dynamic display and respond when an object changed color or onset abruptly. Scan strategies were also evaluated. In another experiment participants were instructed to use particular strategies to detect changes.

RESULTS

Consistent with previous results, onset events were detected better than were color change events. Scan strategy accounted for a large proportion of variance in detection performance. Participants who made few eye movements performed best. Participants who actively scanned the display performed worst. When poor performers were instructed to make few eye movements, their performance matched that of the best performers.

CONCLUSION

Onset alerts can be an effective means of signaling important events in complex displays. Additionally, scan strategy plays an important role in the detection of transient events.

APPLICATION

These results have important implications for training operators to search for transient changes within dynamic and cluttered displays.

An Onset Advantage without a Preview Benefit: Neuropsychological Evidence Separating Onset and Preview Effects in Search

Visual search is facilitated if half the distractors are presented as a preview prior to the presentation of the target and second set of distractors-the preview benefit [Watson, D. G., & Humphreys, G. W. Visual marking: Prioritizing selection for new objects by top-down attentional inhibition of old objects. Psychological Review, 104, 90-122, 1997]. On one account, the preview advantage is due to automatic capture of attention by the onsets in the second, search display [Donk, M., & Theeuwes, J. Visual marking beside the mark: Prioritizing selection by abrupt onsets. Perception & Psychophysics, 93, 891-900, 2001]. We provide a neuropsychological test of this assertion. We examined onset capture and preview benefits in search in a group of neuropsychological patients with unilateral parietal damage. We demonstrate a normal pattern of performance when patients detected targets defined by onsets relative to those defined by offsets, irrespective of whether the onset target fell contra-or ipsilateral to the lesion. In contrast, there was a normal preview benefit in search only for ipsilesional targets, and preview search was impaired in the contralesional field. The data demonstrate that the preview benefit can dissociate from the onset advantage in search, and that onsets remain strongly weighted for attention even in the contralesional field of patients with parietal lesions.

Visual salience in the change detection paradigm: the special role of object onset

The relative efficacy with which appearance of a new object orients visual attention was investigated. At issue is whether the visual system treats onset as being of particular importance or only 1 of a number of stimulus events equally likely to summon attention. Using the 1-shot change detection paradigm, the authors compared detectability of new objects with changes occurring at already present objects--luminance change, color change, and object offset. Results showed that appearance of a new object was less susceptible to change blindness than changes that old objects could undergo. The authors also investigated whether it is onset per se that leads to enhanced detectability or onset of an object representation. Results showed that the onset advantage was eliminated for onsets that did not correspond with the appearance of a new object. These findings suggest that the visual system is particularly sensitive to the onset of a new object.

Stimulus-driven attentional capture: An empirical comparison of display-size and distance methods

Four experiments examined attentional capture by colour as assessed by two different investigative methods. Subjects performed a visual search task for a vertical-target line embedded among tilted-distractor lines, presented inside 4, 8, or 12 coloured discs. Interestingly, when the colour singleton was task irrelevant, and data were analysed by means of the display-size method combined with the zero-slope criterion, no evidence for attentional capture by colour was found. However, when data were analysed by means of the distance method, which consists of monitoring the spatial relationship between the target and the singleton, results showed that the target was found faster and/or more accurately when it was inside the singleton than when it was in a nonsingleton location. This provided evidence for a stimulus-driven attentional capture. In addition, the application of signal detection methodology showed that attentional capture, as revealed by the distance method, resulted from a perceptual modulation at the singleton location, rather than from a criterion shift. We conclude that, at least with the kind of stimuli used here, the display-size method combined with the zero-slope criterion is less than ideal for investigating how static discontinuities can affect the automatic deployment of visual attention.

Covert shifts of attention precede involuntary eye movements

There is considerable evidence that covert visual attention precedes voluntary eye movements to an intended location. What happens to covert attention when an involuntary saccadic eye movement is made? In agreement with other researchers, we found that attention and voluntary eye movements are tightly coupled in such a way that attention always shifts to the intended location before the eyes begin to move. However, we found that when an involuntary eye movement is made, attention first precedes the eyes to the unintended location and then switches to the intended location, with the eyes following this pattern a short time later. These results support the notion that attention and saccade programming are tightly coupled.

Goal-driven modulation of oculomotor capture

In a recent study, Ludwig and Gilchrist (2002) showed that stimulus-driven oculomotor capture by abrupt onset distractors was modulated by distractor-target similarity: Participants were more likely to fixate an irrelevant onset when it shared the target color. Here we test whether this pattern of performance is the result of (1) inhibition of all items in the distractor color, (2) a response bias to local color discontinuities, or (3) the integration of stimulus-driven abrupt onset signals with goal-driven information about the target features. The results of two experiments clearly support the third explanation. We conclude that oculomotor capture is modulated by, but not contingent upon, top-down control, and our findings argue for an integrative view of the saccadic system.

Moving and looming stimuli capture attention

Attention capture is often operationally defined as speeded search performance when an otherwise nonpredictive stimulus happens to be the target of a visual search. That is, if a stimulus captures attention, it should be searched with priority even when it is irrelevant to the task. Given this definition, only the abrupt appearance of a new object (see, e.g., Jonides & Yantis, 1988) and one type of luminance contrast change (Enns, Austen, Di Lollo, Rauschenberger, & Yantis, 2001) have been shown to strongly capture attention. We show that translating and looming stimuli also capture attention. This phenomenon does not occur for all dynamic events: We also show that receding stimuli do not attract attention. Although the sorts of dynamic events that capture attention do not fit neatly into a single category, we speculate that stimuli that signal potentially behaviorally urgent events are more likely to receive attentional priority.

Attentional capture by auto- and allo-cues

In a host of studies, the ability of various types of cues to capture attention has been examined. This article reviews a number of these studies by organizing them into a classification scheme based on the relationship between the putative attention-capturing item (the cue) and the item used to assess the distribution of attention (the probe). The second dimension of this taxonomy divides paradigms of attentional capture into those in which capture is indexed by performance benefits and those in which capture is indexed by performance costs. The relative methodological merits and disadvantages of the paradigms that occupy each of the cells of the resulting two-by-two matrix are discussed. A final section offers a new interpretation of the finding that dynamic cues capture attention.

Contingent visual marking by transients

Preview search is a phenomenon in which a set of new items can be searched with seemingly no interference from items already present in the display. The preview effect has been shown to occur only when the presentation of the new items is accompanied by a luminance change (Donk & Theeuwes, 2001). In a series of experiments, we extend the type of transients that can lead to a preview benefit to offsets and motion, and confirm Donk and Theeuwes's finding that equiluminant color changes do not lead to a preview effect. Like Donk and Theeuwes, we find that preview search does not occur when only the old items undergo a transient change, suggesting that the processes responsible for preview search are triggered when the new items undergo a change detectable by the magnocellular system. In addition, we find that irrelevant transients interfere with preview search only when they match the current attentional set (e.g., luminance change or motion). Results suggest that preview search is not the automatic capture of attention by transients, but rather is contingent on top-down control settings.

Visual marking and visual change

Five experiments investigated the types of changes that disrupt the preview effect--the benefit gained in difficult search tasks from presenting some distractors earlier in time. A shape change with or without an overall luminance change at the location of an old item was found to disrupt the preview effect, whereas an equivalent luminance change alone or an isoluminant color change was not disruptive. Results suggest that (a) relatively low-level visual changes may not be sufficient to abolish the benefit, (b) the benefit most likely occurs through inhibition applied to locations within a location master map, and (c) inhibition need not be applied to surface features of objects.

Attentional guidance of the eyes by contextual information and abrupt onsets

Contextual cuing is a memory-based phenomenon in which previously encountered global pattern information in a display can automatically guide attention to the location of a target (Chun & Jiang, 1998), leading to rapid and accurate responses. What is not clear is how contextual cuing works. By monitoring eye movements, we investigated the roles that recognition and guidance play in contextual cuing. Recognition does not appear to occur on every trial and sometimes does not have its effects until later in the search process. When recognition does occur, attention is guided straight to the target rather than in the general direction. In Experiment 2, we investigated the interaction between memory-driven search (contextual cuing) and stimulus-driven attentional capture by abrupt onsets. Contextual cuing was able to override capture by abrupt onsets. In contrast, onsets had almost no effect on the degree of contextual cuing. These data are discussed in terms of the role of top-down and bottom-up factors in the guidance of attention in visual search.

Influence of single and multiple onset distractors on visual search for singleton targets

In three experiments, we examined attentional and oculomotor capture by single and multiple abrupt onsets in a singleton search paradigm. Subjects were instructed to move their eyes as quickly as possible to a color singleton target and to identify a small letter located inside of it. In Experiment 1, task-irrelevant sudden onsets appeared simultaneously on half the trials with the presentation of the color singleton target. Response times (RTs) were longer when onsets appeared in the display regardless of the number of onsets. Eye-scan strategies were also disrupted by the appearance of the onset distractors, although the proportion of trials on which the eyes were directed to the onsets was the same regardless of the number of onsets. In Experiment 2, we manipulated the time of presentation of two task-irrelevant onsets in order to further examine whether multiple onsets would be attended and fixated prior to attending a color singleton target. Again, subjects made a saccade to a task-irrelevant onset on a substantial proportion of trials prior to fixating the target. However, saccades to the second onset were rare. Experiment 3 served as a replication of Experiment 1 but without the requirement for subjects to move their eyes to detect and identify the singleton target. The RT results were consistent with those in Experiment 1; dual onsets had no larger an effect on response speed than single onset distractors. These data are discussed in terms of the interaction between top-down and bottom-up control of attention and the eyes.

Attention and performance

Recent progress in the study of attention and performance is discussed, focusing on the nature of attentional control and the effects of practice. Generally speaking, the effects of mental set are proving more pervasive than was previously suspected, whereas automaticity is proving less robust. Stimulus attributes (e.g. onsets, transients) thought to have a "wired-in" ability to capture attention automatically have been shown to capture attention only as a consequence of voluntarily adopted task sets. Recent research suggests that practice does not have as dramatic effects as is commonly believed. While it may turn out that some mental operations are automatized in the strongest sense, this may be uncommon. Recent work on task switching is also described; optimal engagement in a task set is proving to be intimately tied to learning operations triggered by the actual performance of a new task, not merely the anticipation of such performance.

Visual marking beside the mark: prioritizing selection by abrupt onsets

In a standard visual marking experiment, observers are presented with a display containing one set of elements (old elements) followed after a certain time interval by a second set of elements (new elements). The task of observers is to search for a target among the new elements. Typically, the time to find the target depends only on the number of new elements in the display and not on the number of old elements, showing that observers search only among the new elements. This effect of prioritizing new elements over old elements is explained in terms of top-down inhibition of old objects-that is, visual marking (Watson & Humphreys, 1997). The present study addressed whether this prioritizing is in fact mediated by top-down inhibition of old objects, as suggested by Watson and Humphreys (1997), or whether it is mediated by the abrupt onsets of the newly presented elements (Yantis & Jonides, 1984). In three experiments, the presentations of the old and new elements were or were not accompanied by a luminance change. The results showed that if new elements were equiluminant with the background, no visual marking occurred, suggesting that new elements must have a luminance onset in order to be prioritized over old elements. Implications for current theories on visual selection are discussed.

Attentional capture by color without any relevant attentional set

The aim of the present study was to investigate mechanisms underlying attentional capture by color. Previous work has shown that a color singleton is able to summon attention only in the presence of a relevant attentional set, whereas when a color singleton is not useful for a task, evidence for purely stimulus-driven attentional capture is controversial. Three visual search experiments (T-L task) were conducted using a method different from that based on set sizes, consisting of monitoring target-singleton distance in a unique display size. In Experiment 1, we demonstrated that attention can be summoned in a real stimulus-driven manner by an irrelevant color singleton. Experiment 2A extended this observation, showing that the color singleton attracted attention even when capture was detrimental. However, Experiment 2B showed that such capture can be strategically prevented. Finally, in Experiment 3, we examined whether such a capture was due to a spatial shift or to a filtering cost, providing evidence supporting the shift hypothesis. Stimulus-driven capture was observed when color was neither the defining nor the reported target attribute (Yantis, 1993) and when subjects naive of visual search tasks were used. The present results give experimental support to many contemporary models of visual attention.

Color, form and luminance capture attention in visual search

Extant models of visual attention predict that a salient element should produce a bottom-up activation leading to a stimulus-driven attentional capture (e.g. Cave, 1999). However, apart from onset, previous works manipulating set-size in visual search failed to provide empirical evidence for this kind of capture. By varying target-singelton distance method, based on a single set-size, we explored whether, in a serial search task, an attentional capture is triggered by static discontinuities such as those generated through the manipulation of color, form, and luminance. The results suggest that those physical properties are indeed able to capture attention automatically.

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.