Verb retrieval in brain-damaged subjects: 2. Analysis of errors

Verb retrieval for action naming was assessed in 53 brain-damaged subjects by administering a standardized test with 100 items. In a companion paper ( Kemmerer & Tranel, 2000), it was shown that impaired and unimpaired subject s did not differ as groups in their sensitivity to a variety of stimulus, l exical, and conceptual factors relevant to the test. For this reason; the m ain goal of the present study was to determine whether the two groups of su bjects manifested theoretically interesting differences in the kinds of err ors that they made. All of the subjects' errors were classified according t o an error coding system that contains 27 distinct types of errors belongin g to five broad categories-verbs, phrases, nouns, adpositional words, and " other" responses. Errors involving the production of verbs that are semanti cally related to the target were especially prevalent for the unimpaired gr oup, which is similar to the performance of normal control subjects. By con trast, the impaired group had a significantly smaller proportion of errors in the verb category and a significantly larger proportion of errors in eac h of the nonverb categories. This relationship between error rate and error type is consistent with previous research on both object and action naming errors, and it suggests that subjects with only mild damage to putative le xical systems retain an appreciation of most of the semantic, phonological, and grammatical category features of words, whereas subjects with more sev ere damage retain a much smaller set of features. At the level of individua l subjects, a wide range of ''predominant error types" were found, especial ly among the impaired subjects, which may reflect either different action n aming strategies or perhaps different patterns of preservation and impairme nt of various lexical components. Overall, this study provides a novel addi tion to the existing literature on the analysis of naming errors made by br ain-damaged subjects. Not only does the study advance our knowledge of the relatively underinvestigated topic of action naming errors, but it also app roaches the analysis from the point of view of a detailed, theoretically mo tivated, and reliable error coding system. (C) 2000 Academic Press.