Verbal fluency characteristics of normal and aphasic speakers.

Fourteen mildly aphasic and 14 normal speakers responded to an oral verbal fluency task for five different semantic categories. Retrieved words were scored within each 15-s time interval of a 60-s task as highly representative (i.e., having a high frequency of occurrence in a previous normative study), moderately representative (i.e., having a moderate frequency of occurrence), or highly unrepresentative (i.e., having a low frequency of occurrence). Both speaker groups were affected similarly by category type, and both retrieved words according to prior data-based notions of semantic categorical organization. The two groups differed with respect to the interaction between time intervals and representativeness levels. The different verbal fluency performance of the aphasic subjects was related to both the temporal occurrence of a word within a 60-s response interval and to its representativeness level (prototypicality) within a particular semantic category.