Academic journal article Psychonomic Bulletin & Review

It's under Control: Top-Down Search Strategies Can Override Attentional Capture

Academic journal article Psychonomic Bulletin & Review

It's under Control: Top-Down Search Strategies Can Override Attentional Capture

Article excerpt

Bacon and Egeth (1994) proposed that observed instances of attentional capture by feature single-tons (e.g., color) were the result of a salience-based strategy adopted by subjects (singleton detection mode) and, thus, were not automatic. They showed that subjects could override capture by adopting strategies based on searching for specific target features (feature search mode). However, Theeuwes (2004) has recently argued that Bacon and Egeth's results arose from experimental confounds. He elaborated a model in which attentional capture must be expected when salient distractors fall within a spatial window of attention. According to Theeuwes's (2004) model, there exist two essential criteria for examining stimulus-driven capture. First, search latencies cannot increase with display size, since the search must be parallel; second, the salience of the irrelevant distractor must not be compromised by characteristics of the search display. Contrary to the predictions of Theeuwes's (2004) model, we provide evidence that involuntary capture can be overridden when both of these criteria are met. Our results are consistent with Bacon and Egeth's proposal.

In a recent article entitled "Top-Down Search Strategies Cannot Override Attentional Capture," Theeuwes (2004; see also 1991a, 1992) argued against the popular notion that featurally salient information in the visual scene can be ignored when it does not match the attentional set of the observer. He claimed, rather, that the selection of sensory information is always granted preferentially to the most salient stimulus within a spatially defined window of attention. As a result, when subjects are engaged in parallel processing, salient distractors should automatically capture attention.

At face value, it may seem difficult to reconcile this account with a great deal of research on attention. Visual search studies have, for decades, shown that the manner in which stimuli are prioritized for selection is dramatically influenced by the observer's strategic goals (e.g., Green & Anderson, 1956), and virtually all recent models of attention incorporate a major component of top-down control (e.g., Wolfe, 1994). Furthermore, numerous studies, employing various experimental designs, have shown that irrelevant, featurally salient distractors do not automatically impair subjects' performance on visual search tasks (e.g., Folk, Leber, & Egeth, 2002; Folk, Remington, & Johnston, 1992; Lamy & Tsal, 1999; Theeuwes, 1990; Yantis & Egeth, 1999). These studies have been widely interpreted to support the contingent capture hypothesis advanced by Folk and colleagues (e.g., Folk et al., 2002; Folk et al., 1992), which states that the degree to which a salient stimulus involuntarily captures attention is dependent on the degree to which that item matches the observer's attentional set.

Inside the Window: A Clarification of Theeuwes's Position

Do the myriad findings of selectivity in the literature counter Theeuwes's (2004) assertion that feature single-tons automatically capture attention? Perhaps not. Critically, Theeuwes (2004) made a distinction between objects that fall inside a window of attention-much like a spotlight (see Posner, Snyder, & Davidson, 1980)-and those that do not. Within the window, objects compete in parallel for selection, and this competition is based purely on salience, so that the most salient item wins the highest processing priority (e.g., Theeuwes, 1991a, 1992, 2004). Objects outside the window, however, do not necessarily compete for selection and can, therefore, be ignored (see Theeuwes, 1990, 1991b; Theeuwes & Burger, 1998). Thus, Theeuwes's brand of automaticity applies not to all stimuli impinging upon the retina but, rather, only to those falling inside an attentional window.

One essential facet of Theeuwes's (2004) model is that the attentional window can vary in size much like the zoom lens proposed by Eriksen and Yeh (1985). …

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