In recent years, there have been numerous reports of patients with brain damage who show selective identification or recognition deficits for objects from specific categories (see Forde, in press; Humphreys & Forde, 2000, for reviews). The most common deficit appears to be a selective impairment in the identification of living things, accompanied by relatively unimpaired recognition or identification of artificial or non-living objects. However, despite the large number of reported cases with category-specific processing deficits, there is still no agreement on the mechanisms that produce these deficits. It is not even clear whether all such cases can be understood in terms of a single process or mechanism, or whether categoryspecific deficits can be caused by a variety of different factors. In this chapter, we explore category-specific deficits from a theoretical viewpoint that evolved from recent research on perceptual categorization and identification. Although some efforts have been made to model category-specific deficits with connectionist models (e.g., Farah & McClelland, 1991; Humphreys, Lamote, & Lloyd-Jones, 1995), we are not aware of any attempts to apply classical models of categorization and identification1 to the neuropsychological data on category-specificity (with the exception of a study by Dixon, Bub, & Arguin, 1997, which will be discussed in detail later)
