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.

Rhythm perception is assumed to be guided by a domain-general auditory principle, the Iambic/Trochaic Law, stating that sounds varying in intensity are grouped as strong-weak, and sounds varying in duration are grouped as weak-strong. Recently, Bhatara et al. (2013) showed that rhythmic grouping is influenced by native language experience, French listeners having weaker grouping preferences than German listeners. This study explores whether L2 knowledge and musical experience also affect rhythmic grouping. In a grouping task, French late learners of German listened to sequences of coarticulated syllables varying in either intensity or duration. Data on their language and musical experience were obtained by a questionnaire. Mixed-effect model comparisons showed influences of musical experience as well as L2 input quality and quantity on grouping preferences. These results imply that adult French listeners’ sensitivity to rhythm can be enhanced through L2 and musical experience.

This study provides a novel approach for testing the universality of perceptual biases by looking at speech processing in simultaneous bilingual adults learning two languages that support the maintenance of this bias to different degrees. Specifically, we investigated the Iambic/Trochaic Law, an assumed universal grouping bias, in simultaneous French–German bilinguals, presenting them with streams of syllables varying in intensity, duration or neither and asking them whether they perceived them as strong-weak or weak-strong groupings. Results showed robust, consistent grouping preferences. A comparison to monolinguals from previous studies revealed that they pattern with German-speaking monolinguals, and differ from French-speaking monolinguals. The distribution of simultaneous bilinguals' individual performance was best explained by a model fitting a unimodal (not bimodal) distribution, failing to support two subgroups of language dominance. Moreover, neither language experience nor language context predicted their performance. These findings suggest a special role for universal biases in simultaneous bilinguals.