Information processing in a binary classification task

Three choice-reaction time studies were conducted to investigate whether information processing is exhaustive or self-terminating, serial or parallel, and N-dependent or N-independent. A total of 54 subjects were required to make key-pressing responses to one, two, or three digits presented in a circular display; one key was pressed if the display contained one or more target digits and another key was pressed if the display contained only nontarget digits. The first two studies utilized within-subjects designs in which the displays were constructed from only one target and one nontarget item (Study 1) or from three target and seven nontarget items (Study 2). The third study used a between-subjects design in which different groups of subjects responded to one-, two-, or three-element displays. In general, the results indicate that CRTs increased as the total number of display elements increased and decreased as the number of target elements (or the ratio of target to nontarget items) increased for a given display size. When only target elements were presented, CRT was independent of the number of elements displayed, and when only one target was presented, CRT increased as total number of elements increased. Theses combined results are interpreted as support for the inference that information processing in visual search tasks tends to be self-terminating, serial, and N-dependent (of limited capacity).