Neural entrainment to speech in theta range is affected by language properties but not by the native language of the listeners

A universal speech rhythm around 5 Hz, corresponding to syllable beats, is captured by neural oscillations in the human brain. However, there is significant variability in syllabic complexity across languages: some languages allow only simple syllables, while some allow more variation (a variation related to linguistic rhythm). Behavioral evidence suggests that humans show different patterns of speech segmentation depending on the linguistic rhythm of their native language. Here, we tested if the entrainment of neural oscillations in the theta range (3-8 Hz) to sentences of languages representative of different linguistic rhythms depends on participants native language rhythm or rather reflects language-specific rhythmic properties. We recorded EEG in two groups of participants: native speakers of English (stress-timed, Experiment 1) and native speakers of Spanish (syllable-timed, Experiment 2). Both groups listened to saltanaj resynthesized sentences from English (stress-timed), Spanish (syllable-timed) and Japanese (mora-timed), a procedure that removes comprehension but keeps language-specific phonological properties. Phase locking value between sentence envelopes and EEG showed the same pattern regardless of participants native language: lowest for English, intermediate for Spanish, and highest for Japanese. Our results suggest that entrainment to speech in the theta frequency range is sensitive to differences in variation in syllabic complexity across languages.