Does language similarity affect representational integration?

Previous studies have suggested that multilingual speakers do not represent their languages entirely separately but instead share some representations across languages. To determine whether sharing is affected by language similarity, we investigated whether participants' tendency to repeat syntax across languages was affected by language similarity. In three cross-linguistic structural priming experiments, trilingual Mandarin-Cantonese-English participants heard a sentence in Cantonese or English (which they matched to a picture) and then described a dative event in Mandarin. When prime and target sentences involved different actions (Experiment 1), structural priming was unaffected by language similarity. But when prime and target involved the same action (Experiments 2 and 3), priming was stronger between related languages (i.e., Cantonese to Mandarin) than unrelated languages (i.e., English to Mandarin). Similar languages are not more integrated than dissimilar languages overall, but the representations that connect lexical and syntactic information are more closely integrated.