Searching for conjunctively defined targets.

It has recently been proposed that in searching for a target defined as a conjunction of two or more separable features, attention must be paid serially to each stimulus in a display. Support for this comes from studies in which subjects searched for a target that shared a single feature with each of two different kinds of distractor items (e.g., a red O in a field of black Os and red Ns). Reaction time increased linearly with display size. We argue that this design may obscure evidence of selectivity in search. In an experiment in which the numbers of the two distractors were unconfounded, we find evidence that subjects can search through specified subsets of stimuli. For example, subjects told to search through just the Os to find the red O target do so without searching through Ns. Implications of selective search are discussed.