Academic journal article Perception and Psychophysics

Consequences of Display Changes during Interrupted Visual Search: Rapid Resumption Is Target Specific

Academic journal article Perception and Psychophysics

Consequences of Display Changes during Interrupted Visual Search: Rapid Resumption Is Target Specific

Article excerpt

Visual search can be resumed more rapidly following a brief interruption to an old display than it can be initiated on a new display, pointing to a critical role for memory in search (Lleras, Rensink, & Enns, 2005). Here, we examine how this rapid resumption is affected by changes made to the display during the interruption of search. Rapid resumption was found to depend on the prior presentation of the target, not merely the distractor items (Experiment 1), and was unaffected by the relocation of all distractor items (Experiment 2). Further, whereas changes to response-irrelevant features of the target did not eliminate rapid resumption (Experiment 3), changes to response-relevant features did (Experiment 4). These results point to the target specificity of rapid resumption and are consistent with reentrant theories of visual awareness.

Recent findings have begun to clarify the role that various memory systems play in visual search. For example, there is now significant evidence that spatial working memory is recruited during visual search (e.g., Oh & Kim, 2004; Woodman & Luck, 2004) and it is most likely involved in keeping track of spatial locations that have been visited by attention (e.g., McCarley, Wang, Kramer, Irwin, & Peterson, 2003; Peterson, Kramer, Wang, Irwin, & McCarley, 2001; Takeda & Yagi, 2000). It also appears to be involved in the planning of which locations to attend next, as though search was based on a "foraging facilitator" mechanism (Klein & McInnes, 1999). Meanwhile, executive working memory is also recruited during visual search tasks (e.g., Han & Kim, 2004), most likely as a means for keeping task instructions active in working memory and for maintaining a visual image or "template" of the target that can be used to influence the deployment of attention in the scene (e.g., Downing, 2000; Fockert, Rees, Frith, & Lavie, 2001). But it is also important to note that not everything is remembered in search. For example, participants do not make use of information about rejected distractors (Horowitz & Wolfe, 1998, 2001, 2003), pointing to an important limit in the nature of what is remembered during search.

In a recent study, Lleras, Rensink, and Enns (2005) used an interrupted search paradigm to demonstrate yet another contribution of memory. In that task, participants were presented with only brief glimpses of the search display (typical "look" times were 100 msec), with these glimpses alternating with blank screens of longer durations (typical "wait" times were 900 msec). Despite the difficulty of this task, participants were generally very good at completing it: participants correctly identified the target after only three presentations of the display on more than 75% of the trials and with accuracy levels above 95%. The most surprising aspect of their performance, in light of current theories, was that participants often showed extremely short response latencies to target identification following re-presentation of the display (below 400 msec), a finding Lieras et al. referred to as rapid resumption.

To be certain, not all responses following interruptions were fast. A more detailed analysis of the response time (RT) distributions showed that, following interruptions, there appeared be two distinct phases: an early phase peaking in the range of 200-300 msec, and a later phase peaking in the range of 600-800 msec. As an illustration, Figure 1 (based on data from lieras et al., 2005) shows the RT distributions following the first presentation of an interrupted search display (panel A), and following all subsequent re-presentations of the search display (panel B). lieras et al. interpreted the early phase (rapid resumption) as evidence that some perceptual preprocessing1 of the search display had occurred during the preceding look. As a result, fast RTs were observed whenever that preprocessing included information about the target, whereas slower RTs were observed otherwise. …

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