When Syntax Needs Semantics: A Cross-linguistic Time–Frequency Analysis of Cantonese and English

This study investigates whether syntactic unification, the process whereby lexical items are combined into a structured sentence representation, operates independently of semantic influence in Cantonese. Specifically, we compared Cantonese with English to examine whether the autonomy of syntactic unification from semantic context is preserved across typologically distinct languages. Prior research has revealed that syntactic unification operates independently of semantic coherence in English and other typologically similar languages, which provide sufficient morphosyntactic cues for structural construction. However, it remains unclear whether such autonomy can be maintained in Cantonese, a language with limited morphosyntactic cues. To address this issue, we conducted a time-frequency analysis focusing on low-beta synchronization (15-20 Hz) as a neural index of syntactic unification. Native speakers of Cantonese (n = 30) and English (n = 30) read three types of sentences: (a) correct sentences, which were syntactically and semantically well-formed; (b) syntactic prose, which were syntactically well-formed but semantically anomalous; and (c) random word strings, which lacked syntactic structure. In English, both correct and prose sentences elicited comparable increases in beta power relative to random strings, consistent with previous findings, indicating that English syntactic unification operates largely independently of semantic coherence. In Cantonese, beta power increases were observed only for correct sentences, with no significant difference between syntactic prose and random word strings. These results suggest that syntactic unification in Cantonese is guided by semantic context, unlike in English, indicating that its autonomy is not universal and is likely constrained by structural cues in the language.