Lexical decision task on French target words: Effect of listeners’ knowledge of the babble-language

• We examine interference occurring during the speech-in-speech situation.
• Intelligible background speech led to linguistic and acoustic interferences.
• Unintelligible background speech produced only acoustic interference.
• L2 background speech led to longer RTs than L1 background speech.

This research examines the nature of the interference that occurs during speech-in-speech processing for late bilingual listeners. Native French-speaking listeners with Italian as their L2 performed a lexical decision task with French target words presented amid background speech (i.e., 4-talker babble) and nonspeech background noise (i.e., speech-shaped fluctuating noise). We compared the masking effects of babble generated in the listeners’ L1 (French), their L2 (Italian), or an unknown language (Irish) to the masking effects of corresponding fluctuating noise. The fluctuating noise contained spectro-temporal information similar to babble but lacked linguistic information. This design allowed us to compare lexical decision times obtained with the 2 kinds of background noise in each language and thus to assess the linguistic interference caused by babble. Results revealed that babble spoken in the known languages (French and Italian) produced both linguistic and acoustic interference and that babble spoken in the unknown language (Irish) produced acoustic interference only. Furthermore, the L1-French L2-Italian listeners were more strongly affected by the L2 babble than by the L1 babble.