Adult Dichotic Processing Differences Relate to Bilingual Induction-Age

Abstract

Adult bilingual subjects (N equals; 40) and monolingual controls (N equals; 40) were recruited for testing on two dichotic listening tasks: (1) a divided-attention task for processing digit names (0-9) and (2) a focused-attention task for processing consonant-vowel (CV) combinations. Subjects were subsequently grouped according to bilingual Induction-Age (i.e., preschool-induction, school-age-induction, post-pubertal-induction and no-induction). Early-induction bilinguals showed a laterality measure comparable to monolinguals, whereas later-induction bilinguals (i.e., school-age and post-pubertal) showed a larger right ear advantage for digits suggesting more left hemisphere involvement. No laterality differences were evident using a CV index. Memory capacity for processing digits was somewhat reduced the earlier the induction of bilingualism in directed attention and attention switching conditions. On voiced CVs the monolinguals showed better processing of alveolars compared to velars; none of the bilingual groups showed this difference. On the unvoiced CVs, bilinguals with school-age induction showed a flattening effect with no difference between their detection of bilabials, alveolars and velars; all other groups showed alveolars superior to velars, which in turn were superior to bilabials. Implications for theory and research are discussed.

Keywords:

• Bilingualism
• information-processing
• dichotic listening
• memory
• neuropsychology
• voicing
• place