Speech perception in bilingual contexts: Neuropsychological impact of mixing languages at the inter-sentential level

Abstract

Abstract The neuropsychological impact of processing naturalistic speech streams containing code switches at the inter-sentential level was studied in fluent bilinguals who frequently switch between languages. To this end, electroencephalographic recordings (EEG) and a behavioral recall test were used to address speech perception while processing pieces of information conveyed in a single- or mixed-language speech carrier. Measurements of spectral power in the continuous EEG signal accompanying perception of speech were directly compared between conditions. The direction of the switch was also assessed. Our principal finding was a reduced oscillatory power in the beta frequencies when bilinguals are attentively listening to informative speech streams in which the two known languages are intermixed. The memory recall test showed equivalent performance across the different language conditions. These results suggest that the cognitive cost of processing speech containing inter-sentential language switches is reflected at a neural level but that it has no measurable impact on the recall of long streams of information. Listening speech in which the two languages known to a bilingual are mixed at a sentence level, may have no clear behavioral drawback, but implies some neural processing cost.