Native language affects rhythmic grouping of speech

Perceptual attunement to one's native language results in language-specific processing of speech sounds. This includes stress cues, instantiated by differences in intensity, pitch, and duration. The present study investigates the effects of linguistic experience on the perception of these cues by studying the Iambic-Trochaic Law (ITL), which states that listeners group sounds trochaically (strong-weak) if the sounds vary in loudness or pitch and iambically (weak-strong) if they vary in duration. Participants were native listeners either of French or German; this comparison was chosen because French adults have been shown to be less sensitive than speakers of German and other languages to word-level stress, which is communicated by variation in cues such as intensity, fundamental frequency (F0), or duration. In experiment 1, participants listened to sequences of co-articulated syllables varying in either intensity or duration. The German participants were more consistent in their grouping than the French for both cues. Experiment 2 was identical to experiment 1 except that intensity variation was replaced by pitch variation. German participants again showed more consistency for both cues, and French participants showed especially inconsistent grouping for the pitch-varied sequences. These experiments show that the perception of linguistic rhythm is strongly influenced by linguistic experience.