Investigations into the locus of language-switching costs in older adult bilinguals

Language switching was studied with older adult (age 65 years and older) and young adult (18-24 years) bilinguals in a blocked-language or mixed-language condition. Results revealed small differences in reaction time (RT) between older adults and college-age participants in the blocked condition. However, older adults showed much slower RTs in the mixed condition which involves sustained switching relative to young adults. In Experiment 2, the same design was used except that participants were asked to translate an auditory word. In this condition, older adults showed a slowing effect but to a much lesser degree. Furthermore, comparisons within the mixed condition (transient switching) revealed that switching costs varied across languages and age groups. The results from the picture-naming task are consistent with models that predict deficiencies in task-set shifting in older adults especially when a stimulus activates multiple responses. Furthermore, the results indicate interesting differences in sustained and transient switching depending on the task.