Assessing the automaticity of the exogenous orienting of tactile attention

We examined whether or not abrupt tactile onsets are capable of exogenously capturing tactile spatial attention when visual spatial attention is focused elsewhere. In experiment 1, we compared performance under dual-task conditions (where participants performed a tactile exogenous cuing task and a rapid serial visual presentation--RSVP--task at the same time) with their performance under single-task conditions (where the participants had to perform only the cuing task, although the RSVP stream was still presented in the background) and to a no-stream condition (where only the cuing task was presented). Tactile cuing was completely suppressed in both the dual-task and single-task conditions, showing that exogenous tactile spatial orienting is modulated by visual-spatial attention, which hence appears to be far from truly automatic. In experiment 2, we demonstrated that the abolishment of exogenous tactile orienting was not caused by the transient presentation of abrupt onset stimuli (letters). These results therefore show that exogenous spatial attentional orienting toward abrupt peripheral tactile stimuli is possible as long as perceptual resources are not depleted by a perceptually demanding (RSVP) task.     

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.     

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.     

Attentional capture under high perceptual load

Attentional capture by abrupt onsets can be modulated by several factors, including the complexity, or perceptual load, of a scene. We have recently demonstrated that observers are less likely to be captured by abruptly appearing, task-irrelevant stimuli when they perform a search that is high, as opposed to low, in perceptual load (Cosman & Vecera, 2009), consistent with perceptual load theory. However, recent results indicate that onset frequency can influence stimulus-driven capture, with infrequent onsets capturing attention more often than did frequent onsets. Importantly, in our previous task, an abrupt onset was present on every trial, and consequently, attentional capture might have been affected by both onset frequency and perceptual load. In the present experiment, we examined whether onset frequency influences attentional capture under conditions of high perceptual load. When onsets were presented frequently, we replicated our earlier results; attentional capture by onsets was modulated under conditions of high perceptual load. Importantly, however, when onsets were presented infrequently, we observed robust capture effects. These results conflict with a strong form of load theory and, instead, suggest that exposure to the elements of a task (e.g., abrupt onsets) combines with high perceptual load to modulate attentional capture by task-irrelevant information.     

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 within and between objects

The present study addressed the question whether attentional capture by abrupt onsets is affected by object-like properties of the stimulus field. Observers searched for a target circle at one of four ends of two solid rectangles. In the focused attention condition the location of the upcoming target was cued by means of a central arrowhead, whereas in the divided attention condition, the target location was not cued. Irrelevant abrupt onsets could appear either within the attended or within the non-attended object. The results showed that in the focused attention condition, onsets ceased to capture attention irrespective of whether the onset appeared within an attended object or within a non-attended object.     

Tradeoffs between attentional effects of spatial cues and abrupt onsets

We determined the relative effectiveness and tradeoffs among central, peripheral, and abrupt onset cues in directing attention to a potential target character. Central cues were arrows located at the fixation point, whereas peripheral cues were arrows occurring about 3° away from fixation, near the location of a potential target. These were contrasted with the abrupt onset of an ambiguous part of a character, which later was filled in to reveal a target or a distractor item. Each trial included an arrow cue and an abrupt onset cue, and both expected cue validities and cue-character SOAs were varied factorially. The results showed that, in general, abrupt onsets captured attention more effectively than either central or peripheral arrow cues. However, tradeoffs among separate cue effects indicated that the power of abrupt onsets to capture attention automatically could be overridden by a high-validity spatial cue presented in advance of the onset character. Tradeoffs between the effects of central and abrupt onset cues were additive, indicating that endogenous and exogenous cues have their main effects at different levels in the visual attention system. Peripheral cues and abrupt onsets showed mainly interactive effects, however, consistent with the idea that both types of cues have exogenous components that affect a common pool of attentional resources.     

The suppression of reflexive visual and auditory orienting when attention is otherwise engaged

Two experiments were conducted to examine whether abrupt onsets are capable of reflexively capturing attention when they occur outside the current focus of spatial attention, as would be expected if exogenous orienting operates in a truly automatic fashion. The authors established a highly focused attentional state by means of the central presentation of a stream of visual or auditory characters, which participants sometimes had to monitor. No intramodal reflexive cuing effects were observed in either audition or vision when participants performed either an exogenous visual or auditory orthogonal cuing task together with the central focused attention task. These results suggest that reflexive unimodal orienting is not truly automatic. The fact that cuing effects were eliminated under both unimodal and cross-modal conditions is consistent with the view that auditory and visual reflexive spatial orienting are controlled by a common underlying neural substrate.     

Relative Effectiveness of Central, Peripheral, and Abrupt-onset Cues in Visual Attention

The relative effectiveness of central arrow, peripheral arrow, and abrupt-onset cues was assessed in a character recognition task. On each trial, either a central or a peripheral arrow cue was presented 0, 100, or 200 msec before the appearance of a three-digit display. Two of the digits were “uncamouflaged” from previous figure-eight masks, whereas the third digit appeared abruptly in a previously empty space. Four different groups of subjects were run in factorial combinations of high or low expected validities for arrow and onset cues. In Experiment 1, arrow cues were located centrally, near the fixation point. Abrupt onsets showed larger cost-plus benefits than central arrows, except when subjects expected the central cues to have higher validity than the onsets. In Experiment 2, arrow cues were located peripherally, near the display digits, and abrupt onsets were again more effective in capturing attention except when peripheral cues had higher validity and led the onsets by 100 msec or more. In both experiments, the relative effectiveness of abrupt onsets decreased with arrow SOA. The results were consistent with a model in which automatic and voluntary processes interact in their control of attentional resources.     

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.     

Dissociations of personally significant and task-relevant distractors inside and outside the focus of attention: a combined behavioral and psychophysiological study

Studies of attentional capture by personally significant stimuli have reached inconsistent results, possibly because of improper control of the participants' attention. In the present study, the authors controlled visual attention by using a Stroop-like task. Participants responded to a central color and ignored a word presented either centrally (i.e., at the focus of attention) or peripherally (i.e., outside the focus of attention). Central words led to slower reaction times and larger orienting responses for significant items than for neutral items. These effects largely disappeared when the words appeared in a peripheral location. The peripheral words interfered with performance when they were relevant to task demands. These results indicate that there is a fundamental difference between task-relevant words and personally significant words: The former capture attention even when presented peripherally, whereas the latter do not.     

Abrupt visual onsets and selective attention: voluntary versus automatic allocation

The hypothesis that abrupt visual onsets capture attention automatically, as suggested by Yantis and Jonides (1984) was tested in four experiments. A centrally located cue directed attention to one of several stimulus positions in preparation for the identification of a target letter embedded in an array of distractor letters. In all experiments, one stimulus (either the target or one of the distractors) had an abrupt onset; the remaining letters did not. The effectiveness of the cue was manipulated (varying either its duration or its predictive validity) to test whether abrupt onsets capture attention even when subjects are in a highly focused attentional state. Results showed that onsets do not necessarily capture attention in violation of an observer's intentions. A mechanism for partially automatic attentional capture by abrupt onset is proposed, and the diagnosticity of the intentionality criterion for automaticity is discussed.     

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.     

Abrupt onsets capture attention independent of top-down control settings II: Additivity is no evidence for filtering

Is attentional capture contingent on top-down control settings or involuntarily driven by salient stimuli? Supporting the stimulus-driven attentional capture view, Schreij, Owens, and Theeuwes (2008) found that an onset distractor caused a response delay, in spite of participants’ having adopted an attentional set for a color feature. However, Folk, Remington, and Wu (2009) claimed that this delay reflects separate, nonspatial filtering costs instead, because the onset effects were additive with color-based capture effects, and capture should have caused underadditivity. The present Experiment 1 shows that contingent capture caused by additional color cues is also additive, just like the onset effect. This makes additivity a dubious diagnostic with regard to spatial capture. Experiment 2 demonstrates that it is possible to obtain underadditivity when attention-demanding distractors have sufficient capturing power. Experiment 3 shows that the abrupt onset interference turns into a benefit when the locations of the onset and the target coincide. Together, these results argue in favor of stimulus-driven attentional capture by abrupt onsets.     

Voluntary allocation versus automatic capture of visual attention

Is there a difference in the kind of attention elicited by an abrupt-onset peripheral cue and that elicited by an instruction (e.g., a central arrow cue) to move attention to a peripheral location? In Experiment 1, we found that peripheral cues are no more effective in orienting attention than are central cues. No evidence was found for separable attentional systems consisting of a volitional response to central cues and an automatic response triggered only by peripheral cues. Rather, an identical or similar attentional process seems to be activated by either type of cue, although perhaps in different ways. Peripheral cues seem to have an automatic component, however, in that once attention is engaged by a peripheral cue, it cannot easily be disengaged for refocus elsewhere. In Experiment 2, after several sessions of practice, subjects were able to circumvent automatic attentional capture by an abrupt-onset peripheral cue and to volitionally redirect the focus of attention. Thus, attentional capture by abrupt-onset stimuli is not strongly automatic.     

Does attention alter appearance?

Abrupt onsets in the visual field can change the appearance of subsequent stimuli, according to one interpretation, by engaging an attentional mechanism that increases effective stimulus contrast. However, abrupt onsets can also engage capacity-unlimited and thus attention-independent sensory mechanisms. We conducted a series of experiments to differentiate the sensory and attentional accounts. Observers compared the contrasts of uncued low-contrast peripheral targets with simultaneous targets cued by one of three cue types with different sensory attributes: white or black peripheral abrupt onsets and central gaze direction cues devoid of sensory activity near the target locations. Each cue facilitated the perception of perithreshold targets; however, the white abrupt onsets increased the perceived contrast of suprathreshold targets, whereas the black abrupt onsets tended to reduce the perceived contrast, and the gaze direction cues had no significant effect. The effectiveness of the gaze direction cues in automatically orienting attention was demonstrated in a control experiment in which they consistently speeded response times. The results suggest that sensory interaction, and not attention, is responsible for changes in appearance.     

突现对内源性选择注意的影响

本研究利用空间线索技术的实验模式,考察内源性选择注意与外源性选择注意的相互关系。实验结果表明,外周线索突现可以优先地被加工,但并不是完全高度自动化的;当注意受内源性中央线索引导集中到一个与突现刺激不一致的空间位置时,突现刺激不能引导出自动化的外源性选择注意。     

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.     

内源性注意与外源性注意的跨通道比较

该研究利用空间线索技术的实验模式,考察跨视觉和听觉通道的内源性选择注意与外源性选择性注意的相互关系。实验结果表明：(1)听觉中央线索在较长的SOA(至少500毫秒)条件下,可以引导内源性空间选择性注意;同时外周线索突现也能自动化地吸引部分注意资源。(2)听觉和视觉选择注意是分离的加工通道,但二者之间存在相互联系。     

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.