We spend a lot of time searching for things. If we know what we are looking for in advance, a memory representation of the target will be created to guide search. But if the identity of the search target is revealed simultaneously with the presentation of the search array, is a similar memory representation formed? In the present study, 96 observers determined whether a central target was present in a peripheral search array. The results revealed that as long as the central target remained available for inspection (even if only in iconic memory), observers reinspected it after each distractor was checked, apparently forgoing consolidation of the target into working memory. The present findings challenged the assumption that evaluating items in a search array must involve comparison with a template in working memory.

In the literature about allocation of selective attention, a widely studied question is when will attention be allocated to information that is clearly irrelevant to the task at hand. The present study, by using convergent evidence, demonstrated that there is a trade-off between quantity of information present in a display and the time allowed to process it. Specifically, whether or not there is interference from irrelevant distractors depends not only on the amount of information present, but also on the amount of time allowed to process that information. When processing time is calibrated to the amount of information present, irrelevant distractors can be selectively ignored successfully. These results suggest that the perceptual load in the load theory of selective attention (i.e., Lavie, 2005) should be thought about as a dynamic rate problem rather than a static capacity limitation. The authors thus propose that rather than conceiving of perceptual load as a quantity of information, they should consider it as a quantity of information per unit of time. In other words, it is the relationship between the quantity of information in the task and the time for processing the information that determines the allocation of selective attention. Thus, the present findings extended load theory, allowing it to explain findings that were previously considered as counter evidence of load theory. (PsycINFO Database Record

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The dual-task paradigm is widely used in studying the interaction between visual search and working memory. A number of studies showed that holding items in working memory delays the overall response time (RT) in visual search, but it does not affect the efficiency of search (i.e., the slope of the RT × set size function). Why the memory load merely affects the overall RT? Some researchers proposed that this load-effect on overall RT may be caused by factors that only affect response selection processes, while others argued that it may reflect the effect of visual working memory load on visual search. This study investigated the two competing hypotheses by measuring the threshold stimulus exposure duration (TSED) for successfully fulfilling a search task. Experiment 1 replicated the large overall RT difference with the RT method but only found a small though reliable overall TSED difference with the TSED method. Experiment 2, with better controls, found no TSED difference by manipulating the visual working memory load. Experiment 3 showed that the TSED is not influenced by processes in the response selection stage. The present findings suggest that the overall stimulus processing time in visual search is not affected by visual working memory load and that the effect of memory load on overall RT is largely due to factors affecting response selection alone.

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