Picture naming and verification in aphasic and neurologically normal bilingual speakers of Spanish and English

The two languages of bilingual speakers differ in manner of acquisition, situations of use, and level of proficiency. Normally occurring differences between two languages complicate the interpretation of between language differences measured when assessing bilingual individuals with aphasia. The purpose of this study was to examine crosslinguistic differences in lexical retrieval and knowledge exhibited by neurologically normal bilingual speakers of English and Spanish and individuals with aphasia. Crosslinguistic differences were examined in relation to variability in language use and proficiency. The reference provided by the neurologically normal speakers served as a metric for identifying the linguistic impairment exhibited by individuals with aphasia which, in turn, provided information valuable to understanding normal processes of lexical retrieval. Five individuals with aphasia and 25 neurologically normal Mexican-American native bilingual speakers of Spanish and English participated in this study. Participants completed a series of language history, use, and proficiency measures prior to participation in five experimental tasks: three picture naming tasks (English Spanish, and bilingual) and two picture verification tasks (Spanish and English). Results from the neurologically normal participants revealed statistically significant differences (p < .05) between performance in English and Spanish on the experimental tasks. Performance on the picture naming tasks was interpreted in relation to accuracy, error type, and item difficulty. A significant proportion of the crosslinguistic variance in naming accuracy was accounted for by differences in Spanish use and proficiency. Results from the participants with aphasia, interpreted as individual case studies, revealed varying degrees of linguistic impairment. Interpretation of observed differences between Spanish and English revealed that accurate measurement of type and severity of impairment was dependent on recognizing normal differences between languages (as indicated by the normal referent) relative to language history, use and proficiency. For four of the five participants with aphasia, differences between scores in English and Spanish were attributable to normally occurring differences in linguistic skill. One participant demonstrated a differential impairment as indicated by reduced scores in English inconsistent with expected skill. Implications of the results for participants with aphasia are discussed in relation to assessment practices and understanding underlying processes of lexical retrieval.