Selective visual attention, visual search and visual awareness.

In a previous study, Butter and Goodale (2000) reported that visual search increases the identification of targets relative to distracters. The present series of studies investigated further this effect of search. Search increased identification of Ls when they were targets and decreased their identification when Ls were distracters in concurrent search involving feature conjunctions (Exp. 1). Subjects in Experiment 2 showed increases in sensitivity, but not in response bias, to Ls. Search had a weaker effect on d' for identification of Ts. Increasing the difficulty of searching for Ts or Ls by increasing the number of distracters enhanced identification of targets versus distracters relative to the effect of search involving eight distracters (Exp. 3). Two studies investigated the effects on probe identification of easy search tasks involving differences in stimulus features. In Experiment 4, there were no reliable effects of search on probe identification when targets were distinguished from distracters by straight versus curved lines (Z vs. O). When horizontal and vertical lines were targets and distracters, subjects showed weak and inconsistent effect on probe identification (Exp. 5). These findings, together with results of neurophysiological studies, support the view that executive mechanisms play a role in visual search by augmenting the activity of goal representations in working memory, thus increasing the likelihood of identifying goal stimuli and enhancing the efficiency of visual search.