How do persons with aphasia describe concrete objects?

Abstract

Feature-based models of semantic processing are predicated on the notion that object concepts are constructed through the co-activation of semantic feature knowledge (e.g., Gainotti, 2006; Tyler et al., 2000; Warrington & Shallice, 1984). For example, for the concept DOG, semantic features include visual-perceptual (has fur, has wet nose), motor/action (walks, wags), and functional (guides the blind) information, along with knowledge of superordinate category membership (animal, mammal, canine), encyclopedic information (Lassie was a famous one, cats are afraid of them), and personal associations/opinions (Dogs are my favorite animal.). In fact, accessing such information is thought to activate retrieval of lexical knowledge for naming and learning the particular patterns of feature co-occurrence among different concepts allows us to categorize similar concepts using shared features (e.g., dogs, cats, mice: all breathe, eat, grow → are animals) distinguish similar concepts using distinctive features (dogs wag their tails, mice do not wag) and recognize concepts that are semantically unrelated (e.g., pencils are utensils used for writing and erasing, which are not activities frequently engaged in by dogs). As yet unresolved is whether different types of ‘core’ semantic features may be more salient to identification and differentiation of different concept domains. Is it, as ‘sensory/function’ or sensorimotor-based hypotheses suggest, that disproportionate deficit to living concepts results from deficient processing of visual-perceptual features (e.g., apple: red, round), considered most salient for their differentiation; whereas disproportionate impairment to nonliving concepts results from deficient processing of functional or action features (pencil: used to write and erase) (e.g., Gainotti, 2006; Warrington and Shallice, 1984)? Or is it the interaction among shared and distinctive features across types that results in disproportionately deficient processing between domains, with shared form-function relations being more robust for living concepts, whereas for nonliving concepts it is more distinctive form-function associations (e.g., Tyler et al., 2000)? Debate is ongoing. That said, a number of treatments for individuals with lexical retrieval impairment consequent to stroke-aphasia have been developed to take advantage of the relationship between access to semantic feature knowledge and activation of object names (see Boyle, 2010 and Kiran, 2007 for review). The purpose of this report is to add to the relatively small body of evidence regarding the types of semantic feature knowledge most accessible to those with aphasia and how that knowledge is accessed domains (i.e., living vs. nonliving)