The initial stage of visual selection is controlled by top-down task set: new ERP evidence

Attention, Perception, & Psychophysics, Nov 2010

Salient visual singleton stimuli produce spatial cueing effects indicative of attentional capture only when they match current task sets, suggesting that capture is subject to top-down control. However, such task-set contingent capture effects could be associated with the top-down controlled disengagement of attention from non-matching stimuli that follows their initial bottom-up salience-driven selection. Using the N2pc component as an event-related potential marker of attentional capture, we demonstrate that top-down task set already controls the initial rapid selection of salient visual singleton stimuli prior to any subsequent attentional disengagement. These findings provide new evidence for the primacy of top-down control over bottom-up salience in attentional capture.

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The initial stage of visual selection is controlled by top-down task set: new ERP evidence

Ulrich Ansorge 0 Monika Kiss 0 Franziska Worschech 0 Martin Eimer 0 0 Ulrich Ansorge, Fakultt fr Psychologie, Universitt Wien , Austria ; Institut fr Kognitionswissenschaft, Universitt Osnabrck , Germany ; Birkbeck College , London, UK ; Franziska Worschech, Institut fr Kognitionswissenschaft, Universitt Osnabrck , Germany ; Birkbeck College , London, UK ; Monika Kiss, Birkbeck College , London, UK ; Martin Eimer, Birkbeck College , London, UK 1 ) Faculty of Psychology, Universitt Wien , Liebiggasse 5, 1010 Wien, Austria Salient visual singleton stimuli produce spatial cueing effects indicative of attentional capture only when they match current task sets, suggesting that capture is subject to top-down control. However, such task-set contingent capture effects could be associated with the top-down controlled disengagement of attention from nonmatching stimuli that follows their initial bottom-up salience-driven selection. Using the N2pc component as an event-related potential marker of attentional capture, we demonstrate that top-down task set already controls the initial rapid selection of salient visual singleton stimuli prior to any subsequent attentional disengagement. These findings provide new evidence for the primacy of top-down control over bottom-up salience in attentional capture. - Our visual system has evolved to detect and identify currently relevant objects. Attentional mechanisms play a critical role in visual cognition because they determine which of the many objects that are simultaneously present in the visual world are selected as targets for eye movements, in-depth analysis, and identification. A critical question is whether the attentional selection of visual objects is fully under endogenous top-down control or whether properties of the visual world dictate which objects are selected. Some have claimed that top-down control drives the allocation of attention to different parts of the visual input from the very start (cf. Bichot, Rossi, & Desimone, 2005). Others have argued that endogenous control of attentional selection can only be exerted after an initial phase during which visual stimuli attract attention in an exogenous bottom-up fashion that is determined by salience alone (cf. Bergen & Julesz, 1983; Itti & Koch, 2001). Results from visual search experiments have suggested that perceptually salient but task-irrelevant visual events can capture attention independently of current top-down task sets. When participants search for a shape-defined singleton target among non-target shapes (such as a diamond target among circle distractors), reaction times (RTs) are delayed when a salient but task-irrelevant color singleton is present relative to trials without an additional color distractor (e.g., Theeuwes, 1992). This indicates that color singletons capture attention due to their bottom-up salience and irrespective of current search intentions. However, other studies (e.g., Folk & Remington, 1998; Folk, Remington, & Johnston, 1992; Folk, Remington, & Wright, 1994) have demonstrated that the ability of salient visual events to capture attention is determined by topdown task sets. When spatially uninformative singleton cues precede visual search displays, faster RTs for visual search targets at cued locations indicate attentional capture by these cues. Critically, such spatial cueing effects are only present when cues share features with currently taskrelevant stimuli (e.g., red color singleton cues in blocks where targets are also red), but not when cue features are task-irrelevant. Based on such findings, Folk et al. (1992) proposed their contingent involuntary orienting hypothesis, which postulates that salient visual feature singletons capture attention only when their features match an active top-down attentional setting. Once such a control setting is established (via experimental instructions that specify target-defining visual features), stimuli that share critical properties will attract attention even when they are known to be task-irrelevant (hence involuntary orienting). The hypothesis that attention is captured in a bottom-up fashion by salient visual singletons regardless of their task relevance (Theeuwes, 1992) appears at odds with the observation that spatial cueing effects indicative of attentional capture are absent when singleton cues do not share attributes with targets (Folk et al., 1992). However, Theeuwes and colleagues (Belopolsky, Schreij, & Theeuwes, 2010; Theeuwes, 2010; Theeuwes, Atchley, & Kramer, 2000) have claimed that bottom-up attentional capture is perfectly consistent with results such as those observed by Folk et al. (1992). They argue that visually salient singleton stimuli will always capture attention, regardless of whether they match a currently active task set. Contingent capture effects are the result of top-down control mechanisms that affect selective attentional processing after the initial salience-driven attentional capture. According t (...truncated)


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Ulrich Ansorge, Monika Kiss, Franziska Worschech, Martin Eimer. The initial stage of visual selection is controlled by top-down task set: new ERP evidence, Attention, Perception, & Psychophysics, 2010, pp. 113-122, Volume 73, Issue 1, DOI: 10.3758/s13414-010-0008-3