Studies of perceptual and cognitive matching often find (a) that same judgments are faster than different judgments (the same-different disparity) and (b) that same judgments to physically identical stimuli are faster than those to nominally identical, but physically dissimilar, stimuli (the name-physical disparity). The most widely accepted explanations of these phenomena propose quite different bases for them. The present article develops a single theoretical framework that accounts for both phenomena. Three processes are shown to contribute to the reaction time differences for single-letter pairs: the level of processing at which the match is performed, facilitation in the rate at which repeated stimuli are encoded, and inhibition that occurs when competing name codes are activated. The inhibitory process contributes to both simultaneous and sequential matches. Level of processing, however, contributes only to simultaneous matches, whereas the facilitory process contributes only to sequential matches. The theoretical framework that is developed accounts for the majority of data that have been obtained regarding the same-different and name-physical disparities. Several findings are reinterpreted in terms of the theory. More importantly, the theory serves an integrative role. The relationship between the same-different disparity and the name-physical disparity is clarified, and a wide range of additional phenomena obtained with the matching task are organized within the framework. The theory also relates the matching-task phenomena to more general processing principles apparent in other areas of research.Perceptual and cognitive matching tasks range of issues. These include not only issues have received extensive use in recent years regarding the underlying processes involved (see Nickerson, 1972;Posner, 1978). Such in matching two stimuli (e.g., Krueger, tasks involve either simultaneous or sequen-1978;Miller, 1978; Posner & Mitchell, tial presentation of pairs of stimuli that sub-1967) but also issues of a more general najects judge to be the same or different ac-ture, such as differences in the processing cording to criteria set by the experimenter, of familiar and unfamiliar stimuli (e.g., Am-The dependent variable most commonly bier & Proctor, 1976), attentional demands measured is the time to respond appropri-of processing (e.g., Posner & Boies, 1971; ately to each stimulus pair. Proctor & Fisicaro, 1977), mental manipu-Variations of the matching task have lation of visual patterns (e.g., Metzler & proved to be useful in examining a wide Shepard, 1974), and short-term retention of visual information (e.g., Posner, Boies, Ei-I would like to thank Cecilia Champion and Steve chelman, & Taylor, 1969). Welch for their assistance in conducting the experiments Despite the Wide variety of research conreported in this article. I am particularly grateful to ducted with the matching task, there has Janet Proctor for her careful critiques of the manuscript been little agreement regarding the exact "itaSSR reprints sh...