Cross-linguistic phonetic differences affect lexical co-activation in second-language learners

Introduction When listening to speech in one language, bilinguals have been shown to activate word candidates from both their languages, which then compete for recognition. Similarity between the auditory input and the mental representations is a crucial factor for activation of a candidate. However, similarity is usually defined in terms of phoneme overlap, which might not be fine-grained enough to capture the reality of lexical co-activation and subsequent competition. The present study investigates how subphonemic differences between phonemically identical German–English word pairs influence their co-activation. Methods In a Lexical Decision (LD) experiment with cross-linguistic priming, L1-German learners of English heard an English prime word, followed by a written German target word or non-word and indicated whether the target was a German word or a non-word. Primes and targets showed either no phonemic overlap (Unrelated condition), partial overlap (Similar condition) or full phonemic overlap (Identical condition). In the critical Identical condition, English primes and German targets were phonemically identical—either cognates (e.g., /nεst/“nest”) or Interlingual Homophones (ILHs; e.g., /gɪft/, English “gift” /German “poison”)—but varied in their phonetic similarity due to phonetic differences between the languages. Results A comparison of reaction times (RTs) across all priming conditions revealed opposing effects for cognates and ILHs on the phonemic level: For cognate targets, there was facilitation the more phoneme overlap there was between prime and target, while ILH targets were subject to inhibition with more phoneme overlap between prime and target. A comparison of RTs to items of varying phonetic similarity within the Identical condition revealed similar facilitation effects for cognates and ILHs on the phonetic level: RTs to both decreased as a function of phonetic similarity between prime and target. Discussion These findings suggest differential roles of phonemic and phonetic similarity during the processes of (co-)activation and competition and complex interactions between levels. Implications for models of bilingual speech comprehension are discussed.