Discriminative skill and discriminative matching in perceptual recognition.

An important aspect of any recognition or identification task is one's knowledge of the set of alternative items from which the stimuli are drawn. In general, we can respond most accurately when we have the fullest knowledge of what stimulus events are possible. In many recognition experiments, however, the set of possible stimuli is left ambiguous at first and only after considerable experience in the situation does one become familiar with the range and variety of stimuli that are used and master a set of responses appropriate to them. In such experimental situations there is usually a considerable improvement in performance as one narrows down the initially ambiguous range of possible stimuli to the particular set that is actually presented. At the same time, one's skill as such in recognizing items is improved by practice. Learning to recognize briefly or peripherally exposed materials, or learning to recognize items masked by noise or glare—these are skills that also improve with practice regardless of the items to be recognized. In the present experiment, improvement in knowledge of items to be recognized is measured as a function of S's mastery of the list of stimulus items. Thus two measures were taken, one of the degree to which the 1 This research was supported jointly by the Laboratory of Social Relations and the PsychoAcoustics Laboratory of Harvard University under its ONR Contract N5-ori-76 (Project NR 142-201, PNR-172). stimulus alternatives were known and a second of the accuracy with which these same stimuli could be recognized.