French Speakers Prefer Prosody Over Statistics to Segment Speech

To segment words in unfamiliar speech, listeners are known to exploit both native prosodic cues and statistical cues available in the speech signal. However, how and when these cues are combined remains a matter of debate. Here, we studied how transitional probabilities (TPs) and prosodic phrasal boundaries are combined by French speakers to segment words. Since French does not have lexical stress, prosodic phrasal boundaries unambiguously signal word boundaries, providing a unique possibility to test whether prosodic cues can overcome statistical ones, and constrain further statistically based segmentation. We tested French adults in an artificial speech segmentation task, manipulating the consistency between prosodic and TP cues, signaling either the same or different word boundaries. Results showed that participants favored prosodic phrasal boundaries over TPs, regardless of exposure time to the speech stream (Experiment 1: 3.5 minutes; Experiment 2: 7 min), supporting a prosodically driven statistical segmentation of the speech stream.