Phrase-level speech timing preferences predict synchronization in joint reading.

For rhythmic motor activities, such as tapping, walking, and playing music, individuals often show preferred timescales, and differences between individuals' timing preferences impact how well they can synchronize. Speech is only quasi-periodic, but previous studies have suggested that it also exhibits preferred timescales for linguistic units, e.g., syllables and intonational phrases. The present study provides a direct test of whether individual speech timing preferences at syllable and phrase boundaries constrain synchronization in joint speech. We recorded Mandarin speech while participants read aloud lists of short, regularly structured sentences in solo and joint reading tasks. Syllable-level timing was measured with inter-syllable onset interval, and phrase-level timing was indexed by phrase-final lengthening and inter-phrase pause. Participants (N = 88) completed an at-home solo reading task; a subset (N = 32) participated in an in-lab session with solo and paired joint reading. Results show that mean syllable duration is highly aligned in joint reading, regardless of individuals' preferred syllable duration during solo speech. In contrast, mismatches in individuals' phrase-level, but not syllable-level, timing preferences during solo speech significantly predicted syllable onset asynchrony during joint reading. These findings suggest that syllable timing is adaptable in speech synchronization, while final lengthening and pauses between intonational phrases show stronger individual preferences that impact synchronization performance.