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Shahab Ghorashi, Daniel Smilek, Vincent Di Lollo; Distinct attentional resources subserve visual search and dual tasks. Journal of Vision 2004;4(8):342. doi: 10.1167/4.8.342.
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© ARVO (1962-2015); The Authors (2016-present)
Attentional requirements are commonly assessed using two main paradigms: visual search and dual task. In visual search, observers look for a target among distractors. Search efficiency is indexed by the slope of the function relating response time to the number of distractors. The shallower the slope, the more efficient the search. In dual tasks, observers perform two tasks concurrently. An example is the “attentional blink” (AB) in which identification of the second of two targets is impaired when it is presented at a short temporal lag after the first. Using an AB task, Joseph et al. (1997) concluded that even such putatively “preattentive” attributes as orientation do, in fact, require attention because accuracy was impaired at short lags. We reasoned that if the AB and visual search tapped the same attentional resources, efficiency of visual search should suffer progressively as lag is decreased in the AB. Our procedures were similar to those of Joseph et al.: the first target was a white letter inserted in an RSVP of black letters and the second target was a search display presented at 3 different lags. Our procedures differed from those of Joseph et al. in two main ways: First, the number of distractors in the search displays was varied so as to assess search efficiency at each lag. Second, the search display involved either an orientation-oddball discrimination (which is done efficiently as a single task) or a conjunction search (T among Ls, which is done inefficiently as a single task). We found pronounced AB deficits in both search tasks. Importantly, however, search efficiency was unaffected by lag. We conclude that dual-task and visual search paradigms tap different attentional resources. The dual-task deficit occurs when processing of the secondary target is postponed, leaving it vulnerable to masking. But this does not affect the efficiency with which the secondary target is processed once attention is deployed to it.
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