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.     

Abrupt onsets capture attention independent of top-down control settings

Previous research using a spatial cuing paradigm in which a distractor cue preceded the target has shown that new objects presented with abrupt onsets only capture attention when observers are set to look for them (e.g., Folk, Remington, & Johnston, 1992). In the present study, we used the same spatial cuing paradigm as Folk et al. (1992) to demonstrate that even when observers have an attentional set for a color singleton or a specific color feature, an irrelevant new object presented with an abrupt onset interfered with search. We also show that the identity of the abrupt-onset distractor affects responses to the target, indicating that at some point spatial attention was allocated to the abrupt onset. We conclude that abrupt onsets ornew objects override a top-down set for color. Abrupt onsets or new objects appear to capture attention independently of top-down control settings.     

Attentional capture by globally defined objects.

The abrupt appearance of a new perceptual object in the visual field typically captures visual attention. However, if attention is focused in advance on a different location, onsets can fail to capture attention (Yantis & Jonides, 1990). In the present experiments, we investigated the extent to which the deployment of attention to the local level of a hierarchical scene may be affected by the abrupt appearance of a new object at the global level. Participants searched for a semi-disk target in an array of randomly oriented segmented disks ("pacmen"). On half the trials, a subset of the segmented disks induced a subjective square. On these critical trials, participants were significantly slower to respond to the presence of a local target even though the local features of the display were qualitatively identical across all conditions. This slowing was absent when outline pacmen were used (which do not induce subjective figures) and when the subjective square was perceptually old. When the participants' task was defined at the global level of the display, a new local element failed to capture attention, suggesting an asymmetry in the ability of objects at different levels of a hierarchical scene to capture attention. In a control experiment, a new local element captured attention, however, when the participants' task was defined at the local level, indicating that the local item was in principle capable of capturing attention. It is argued that global objects capture attention because they convey important information about the environment that is not available at the local level.     

Attentional capture by globally defined objects

The abrupt appearance of a new perceptual object in the visual field typically captures visual attention. However, if attention is focused in advance on a different location, onsets can fail to capture attention (Yantis & Jonides, 1990). In the present experiments, we investigated the extent to which the deployment of attention to the local level of a hierarchical scene may be affected by the abrupt appearance of a new object at the global level. Participants searched for a semi-disk target in an array of randomly oriented segmented disks (“pacmen”). On half the trials, a subset of the segmented disks induced a subjective square. On these critical trials, participants were significantly slower to respond to the presence of a local target even though the local features of the display were qualitatively identical across all conditions. This slowing was absent when outline pacmen were used (which do not induce subjective figures) and when the subjective square was perceptually old. When the participants’ task was defined at the global level of the display, a new local element failed to capture attention, suggesting an asymmetry in the ability of objects at different levels of a hierarchical scene to capture attention. In a control experiment, a new local element captured attention, however, when the participants’ task was defined at the local level, indicating that the local item was in principle capable of capturing attention. It is argued that global objects capture attention because they convey important information about the environment that is not available at the local level.     

Change blindness and the primacy of object appearance

A large body of work suggests that the visual system is particularly sensitive to the appearance of new objects. This is based partly on evidence from visual search studies showing that onsets capture attention whereas many other types of visual event do not. Recently, however, the notion that object onset has a special status in visual attention has been challenged. For instance, an object that looms toward an observer has also been shown to capture attention. In two experiments, we investigated whether onset receives processing priority over looming. Observers performed a change detection task in which one of the display objects either loomed or receded, or a new object appeared. Results showed that looming objects were more resistant to change blindness than receding objects. Crucially, however, the appearance of a new object was less susceptible to change blindness than both looming and receding. We argue that the visual system is particularly sensitive to object onsets.     

Perceptual load modulates attentional capture by abrupt onsets

The abrupt appearance of a new object captures attention, even when the object is task irrelevant. These findings suggest that abrupt onsets capture attention in a stimulus-driven manner and are not susceptible to top-down influences on attentional control. However, previous studies examining the ability of abrupt onsets to capture attention have used search displays that lacked significant complexity. Because attention is a limited capacity mechanism, it is possible that increasing the complexity, or perceptual load, of the search arrays may modulate capture by abrupt onsets. We used a flanker task to examine the effect of perceptual load on attentional capture by abruptly appearing objects. Subjects searched for a target letter through low-load (set size=1) and high-load (set size=6) displays. On each trial, irrelevant flankers also appeared, one as an onset and the other as an offset. Onset flankers affected search in low-load but not high-load displays. This modulation of attentional capture was not caused by generalized slowing when subjects searched through high-load displays; search for a single perceptually degraded target slowed response times but did not affect attentional capture. These findings demonstrate that attentional capture by an abrupt onset is attenuated when people search through high-load scenes.     

Can new objects override attentional control settings?

Previous research suggests that attentional capture by abrupt onsets is contingent on top-down attentional control settings. Four experiments addressed whether similar contingencies hold for capture elicited by the appearance of new perceptual objects. In a modified spatial cuing task, targets defined by abrupt onset or color were paired with distractors consisting of an abrupt brightening of an existing object or the abrupt appearance of a new object. In Experiments 1 and 2, when subjects searched for an onset target, both distractor types produced evidence of capture. When subjects searched for a color target, however, distractors produced no evidence of attentional capture, regardless of whether they consisted of a new perceptual object or not. Experiments 3-5 showed that the lack of distractor effects in the color-target condition cannot be accounted for by rapid recovery from capture. It was concluded that attentional capture by new objects is subject to top-down modulation by attentional control settings.     

The interaction between memorized objects and abrupt onsets in oculomotor capture

Recent evidence has been found for a source of task-irrelevant oculomotor capture (defined as when a salient event draws the eyes away from a primary task) that originates from working memory. An object memorized for a nonsearch task can capture the eyes during search. Here, an experiment was conducted that generated interactions between the presence of a memorized object (a colored disk) with the abrupt onset of a new object during visual search. The goal was to compare memory-driven oculomotor capture to oculomotor capture caused by an abrupt onset. This has implications for saccade programming theories, which have little to say about saccades that are influenced by object working memory. Results showed that memorized objects capture the eyes at nearly the same rate as abrupt onsets. When the abrupt onset and a memorized color coincide in the same object, this combination leads to even greater oculomotor capture. Finally, latencies support the competitive integration model: Shorter saccade latencies were found when the memorized color combined with the onset captured the eyes, as compared to either color or onset only. Longer latencies were also found when the color and onset occurred in the same display but were spatially separated.     

Spatial updating of dynamic scenes: Tracking multiple invisible objects across viewpoint changes

Research on dynamic attention has shown that visual tracking is possible even if the observer’s viewpoint on the scene holding the moving objects changes. In contrast to smooth viewpoint changes, abrupt changes typically impair tracking performance. The lack of continuous information about scene motion, resulting from abrupt changes, seems to be the critical variable. However, hard onsets of objects after abrupt scene motion could explain the impairment as well. We report three experiments employing object invisibility during smooth and abrupt viewpoint changes to examine the influence of scene information on visual tracking, while equalizing hard onsets of moving objects after the viewpoint change. Smooth viewpoint changes provided continuous information about scene motion, which supported the tracking of temporarily invisible objects. However, abrupt and, therefore, discontinuous viewpoint changes strongly impaired tracking performance. Object locations retained with respect to a reference frame can account for the attentional tracking that follows invisible objects through continuous scene motion.     

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.     

New objects dominate luminance transients in setting attentional priority.

Both the sudden appearance of an object and sudden changes in existing object features influence priority in visual search. However, direct comparisons of these influences have not been made under controlled conditions. In 5 visual search experiments, new object onsets were compared directly with changes in the luminance of old objects. Factors included the luminance contrast of items against the background, the magnitude of luminance change, and the probability that these changes were associated with the target item. New objects were consistently more effective in guiding search, such that a new item with very low luminance contrast was equivalent to an old item undergoing a large change in luminance. An important exception was an old item changing in contrast and polarity, which was as effective as the appearance of a new object. This indicates that search priority is biased toward object rather than situational changes.     

New objects do not capture attention without a top-down setting: Evidence from an inattentional blindness task

Past studies have suggested that a new object can involuntarily capture attention in a visual search task (Yantis & Jonides, 1984 Yantis, S. and Jonides, J. 1984. Abrupt visual onsets and selective attention: Evidence from visual search. Journal of Experimental Psychology: Human Perception and Performance, 10: 601–621. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]). However, trials in these experiments usually begin with abrupt onsets that are considered to signal new objects; thus, there may be a bias toward paying attention to new objects. We examine whether new objects can still capture attention when this bias is excluded, using an inattentional blindness task. Our results showed that when the trials began with new objects, a new object captured attention. When new objects were totally irrelevant and all top-down settings for new objects were prevented, a new object did not capture attention. Our findings argue against the view that new objects capture attention in a purely stimulus-driven fashion.     

Attentional capture by abrupt onsets and feature singletons produces inhibitory surrounds

Two experiments found that form discriminations to a target item were inhibited when the target appeared adjacent to an attentionally salient item. Experiment 1 manipulated the attentional salience of an irrelevant color singleton through the attentional set adopted by the subjects. Color singletons captured attention when the target was itself a feature singleton, but not when the target was defined as a conjunction of features. Attentional capture was accompanied by an inhibitory region (i.e., slowed target reaction times), which dissipated with distance from the color singleton. In Experiment 2, the attentional salience of abrupt onsets and color singletons was compared. Irrelevant abrupt onsets captured attention, whereas irrelevant color singletons failed to capture attention. Again, an inhibitory region surrounded the attentionally salient abrupt onsets, but not the color singletons. The results are discussed in the context of current models of visual spatial attention and suggest a distinction between attentional preparation and attentional selection.     

Attentional dwelling and capture by color singletons

Can salient stimuli—such as color singletons and abrupt onsets—involuntarily capture spatial attention? We previously reported evidence that abrupt onsets can capture attention, but the effects of this capture can become latent under easy visual search. The present experiments examined whether a similar pattern of latent capture occurs for task-irrelevant color singletons. Participants searched for a perfect circle among oval distractors. We manipulated search difficulty by varying the width of the oval distractors, making them more or less target-like (i.e., more or less circular). With search displays of homogeneous distractors, cue validity effects increased linearly with search difficulty, indicating capture by color singletons (Experiments 1 and 2). With heterogeneous distractors, however, discouraging the use of singleton-detection mode to find the target circle, cue validity effects from color singletons were negligible at all difficulty levels (Experiment 3). Using these exact same heterogeneous search displays, meanwhile, abrupt onsets produced very large cue validity effects (Experiment 4). We conclude that whereas abrupt onsets can capture attention based purely on salience, static color singletons capture attention only when made task-relevant by promoting singleton-detection mode (i.e., contingent capture). The data further support an attentional dwelling account of capture costs and reinforce the recommendation that, to ensure sensitivity to detect the presence (or absence) of attention capture, capture experiments should employ a difficult visual search.

     

旧客体抑制和新客体捕获视角下预览效应的机制

预览效应是一种在已经存在的多个旧客体中优先选择多个新客体, 对新客体表现出优先加工的现象。文章综述了预览效应认知神经机制的两种主要观点：(1)旧客体抑制观点, 认为预览效应是由于对旧客体的抑制; (2)新客体突现捕获注意观点, 认为预览效应是由于新客体出现伴随着亮度突然增加捕获注意。这两种观点之间的主要争论在于：预览效应与新旧客体亮度变化的关系; 新旧客体的颜色关系是否影响对目标的搜索; 在一些因素的作用下, 旧客体形状变化是否还会破坏预览效应。文章指出, 预览效应是旧客体抑制机制与新客体突现捕获注意机制共同作用的结果。     

Perceptual conditions necessary to induce change blindness

Change blindness is a failure to detect a change in an scene when the change occurs along with some visual disturbances. Disturbances are thought to play a delocalizing role that affects the saliency of the “target” transient signal coming from the change location, which would otherwise capture attention and render the change visible. For instance, it is hypothesized that the appearance of new objects in the “mudsplashes” paradigm generates transient signals that compete with the target object's transient signal for attracting attention. Thus, experiments using the mudsplashes paradigm do not rule out a possible role of object changes in capturing attention. Here, by reversing image contrast polarity, we develop a new paradigm to produce change blindness when a real global transient signal is the only visual event occurring, with no edges added or deleted except in the target object. The results show that transient signals, per se, are able to prevent change detection. However, abrupt transients are not necessary if object change occurs in the zero-contrast phase of a smoothly fading and reappearing image, leaving attention as the only common factor affecting all cases of change blindness.     

Offset transients modulate attentional capture by sudden onsets

Recent research with visual search tasks has suggested that stimuli which appear as sudden onsets (new objects) have attentional priority over stimuli that are created by removing segments of premasks (non-onset stimuli). Attentional capture by sudden onsets occurs despite the fact that the appearance of these new objects predicts neither the identity nor the location of the target in the visual search task. In three experiments, we examined the extent to which attentional capture by sudden onsets could be modulated by offset transients used to create non-onset objects. To that end, we systematically manipulated the ratio of non-onset to onset stimuli in the display (display ratio) as well as the ratio of offset to onset segments between the stimulus types (stimulus ratio). Increases in either the stimulus ratio or the display ratio resulted in increases in the visual search slopes for the onset targets. These results suggest that the ability of sudden onsets (new objects) to capture attention is influenced by stimulusdriven factors, such as environmental change. Interestingly, the results also indicated that goal-directed or purposeful search for sudden-onset (new-object) targets was relatively uninfluenced by the amount of change in the visual display. Therefore, it would appear that environmental change has differential effects on goal-directed and stimulus-driven search. These results are discussed in terms of their implications for our understanding of attentional capture.     

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.     

Visual motion and attentional capture

Previous work has shown that abrupt visual onsets capture attention. This occurs even with stimuli that are equiluminant with the background, which suggests that the appearance of a new perceptual object, not merely a change in luminance, captures attention. Three experiments are reported in which this work was extended by investigating the possible role of visual motion in attentional capture. Experiment 1 revealed that motion can efficiently guide attention when it is perfectly informative about the location of a visual search target, but that it does not draw attention when it does not predict the target’s position. This result was obtained with several forms of motion, including oscillation, looming, and nearby moving contours. To account for these and other results, we tested anew-object account of attentional capture in Experiment 2 by using a global/local paradigm. When motion segregated a local letter from its perceptual group, the local letter captured attention as indexed by an effect on latency of response to the task-relevant global configuration. Experiment 3 ruled out the possibility that the motion in Experiment 2 captured attention merely by increasing the salience of the moving object. We argue instead that when motion segregates a perceptual element from a perceptual group, a new perceptual object is created, and this event captures attention. Together, the results suggest that motion as such does not capture attention but that the appearance of a new perceptual object does.