ABSTRACT
For both normal subjects and patients with selective brain lesions, objects belonging to some categories can be particularly hard to recognise and/or to name (for reviews see Caramazza, 1998; Forde, 1999; Forde & Humphreys, 1999; Humphreys & Forde, 2001; Saffran & Schwartz, 1994). Numerous accounts have been offered to explain why these differences in recognition and naming occur, illustrated by the other chapters in this book and discussed in some detail below. In this chapter, we propose that category effects can be determined by a principle of information processing that we term target-competitor differentiation. We argue that processes of response selection, in general, require that target stimuli be differentiated sufficiently from competitors. Differentiation operates dynamically, across time, and concurrently at different levels of representation; in this way, processing at one level can constrain differentiation at other levels. Thus one given process (e.g. name selection) can be facilitated by recruiting information from different sources if it aids the differentiation between a target and its competitors. We argue that differentiation for name selection can draw on various types of information, including functional associations as well as perceptual contrasts between stimuli, and that the differentiation process has pervasive effects on both the nature of our stored representations and on the processes recruited when different tasks are performed. We discuss the implications of targetcompetitor differentiation for object recognition and naming in both
normality and pathology, and the relations between our account and other proposals in the literature.
