Does the processing of first language compounds change in late bilinguals?

It has been suggested that native speakers may develop different grammatical representations and processing patterns in the first language (L1) as they become second language (L2) users. Accordingly, L2 users may diverge from monolinguals in various L1 grammatical domains. The present study investigates potential changes in late bilinguals’ processing of L1 compounds as this will also be revealing for identifying the representation of morphologically complex forms in the bilingual mental lexicon. Crucially, unlike most previous work on L1 attrition, the present study involves late bilinguals living in the home country. Thus the results will uncover the extent of bilingualism effects on the L1 in the L1 setting. In a masked priming experiment, 73 Turkish monolinguals and 34 high-proficiency Turkish-English late bilinguals residing in Turkey were tested on nominal compounds to explore potential monolingualbilingual differences in the processing of L1 Turkish compounds. The results showed that Turkish monolinguals employ decomposition based on the activation of head constituent regardless of semantic transparency of compounds. The bilinguals, however, demonstrated morphemic decomposition based on nonhead constituent only when compounds are fully transparent. These findings suggest that qualitative and quantitative changes may occur in L1 morphological processing of late but highly proficient bilinguals even while residing in the L1 country.