Academic journal article Attention, Perception and Psychophysics

Executive Working Memory Load Does Not Compromise Perceptual Processing during Visual Search: Evidence from Additive Factors Analysis

Academic journal article Attention, Perception and Psychophysics

Executive Working Memory Load Does Not Compromise Perceptual Processing during Visual Search: Evidence from Additive Factors Analysis

Article excerpt

Executive working memory (WM) load reduces the efficiency of visual search, but the mechanisms by which this occurs are not fully known. In the present study, we assessed the effect of executive load on perceptual processing during search. Participants performed a serial oculomotor search task, looking for a circle target among gapped-circle distractors. The participants performed the task under high and low executive WM load, and the visual quality (Experiment 1) or discriminability of targets and distractors (Experiment 2) was manipulated across trials. By the logic of the additive factors method (Sternberg, 1969, 1998), if WM load compromises the quality of perceptual processing during visual search, manipulations of WM load and perceptual processing difficulty should produce nonadditive effects. Contrary to this prediction, the effects of WM load and perceptual difficulty were additive. The results imply that executive WM load does not degrade perceptual analysis during visual search.

Theoretical considerations and empirical evidence suggest that working memory (WM) plays a vital role in visual search (Awh, Vogel, & Oh, 2006). The biased competition model (Desimone & Duncan, 1995) and similar accounts of visual search (Bundesen 1990; Duncan & Humphreys, 1989), for example, posit that an observer holds a target template in visual WM to guide attention while scanning. Consistent with this proposal, dual-task studies have shown that a visual WM load compromises the efficiency of visual search (Oh & Kim, 2004; Woodman & Luck, 2004; Woodman, Luck, & Schall, 2007; but see Woodman, Vogel, & Luck, 2001, for an exception) and that attention is often biased toward stimuli that match the contents of visual WM (Downing, 2000; Olivers, Meijer, & Theeuwes, 2006; Soto, Heinke, Humphreys, & Blanco, 2005; but see Downing & Dodds, 2004; Houtkamp & Roelfsema, 2006; Soto, Humphreys, & Heinke, 2006; and Woodman & Luck, 2007, for evidence of qualifications and exceptions). Perhaps more unexpectedly, search also appears to involve executive WM, the component of the WM system also known to be responsible for such processes as coordinating multiple tasks (e.g., Baddeley, Chincotta, & Adlam, 2001), generating novel behaviors (e.g., Baddeley, Emslie, Kolodny, & Duncan, 1998), inhibiting prepotent responses (e.g., Unsworth, Schrock, & Engle, 2004), and focusing and maintaining attention (e.g., Bleckley, Durso, Crutchfield, Engle, & Khanna, 2003; Conway, Cowan, & Bunting, 2001) (see Baddeley, 2007, and Engle, 2002, for reviews). Research has shown that the demand to maintain a search template can divert executive WM from a concurrent nonvisual task and that the amount of capacity consumed by the template is a function of target complexity (Bourke & Duncan, 2005). Other work has demonstrated the converse pattern of interference, revealing that an executive loading task can reduce search efficiency (Anderson, Mannan, Rees, Sumner, & Kennard, 2008; Han & Kim, 2004) and suggesting again that visual search demands executive WM capacity. Studies of individual differences, moreover, have shown a correlation between WM capacity and performance in search tasks demanding high levels of top-down attentional control, as is needed to suppress salient distractors, for example (Sobel, Gerrie, Poole, & Kane, 2007), or to maintain attentional focus on a subset of items within a field of distractors (Poole & Kane, 2009).

A variety of data thus implicate executive WM as one of the cognitive mechanisms underlying visual search and suggest a number of roles that executive processes might play in search. To further explore the functions of executive WM in visual search, Peterson, Beck, and Wong (2008) examined the influence of executive load on searchers' eye movements. Participants performed a serial search task under single-task control conditions or while concurrently performing an executive WM task. …

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