Syllabic rhythm and prior linguistic knowledge interact with individual differences to modulate phonological statistical learning

Phonological statistical learning - our ability to extract meaningful regularities from spoken language - is considered critical in the early stages of language acquisition, in particular for helping to identify discrete words in continuous speech. Most phonological statistical learning studies use an experimental task introduced by Saffran et al. (1996), in which the syllables forming the words to be learned are presented continuously and isochronously. This raises the question of the extent to which this purportedly powerful learning mechanism is robust to the kinds of rhythmic variability that characterize natural speech. Here, we tested participants with arhythmic, semi-rhythmic, and isochronous speech during learning. In addition, we investigated how input rhythmicity interacts with two other factors previously shown to modulate learning: prior knowledge (syllable order plausibility with respect to participants' first language) and learners' speech auditory-motor synchronization ability. We show that words are extracted by all learners even when the speech input is completely arhythmic. Interestingly, high auditory-motor synchronization ability increases statistical learning when the speech input is temporally more predictable but only when prior knowledge can also be used. This suggests an additional mechanism for learning based on predictions not only about when but also about what upcoming speech will be.

Developmental Changes in Cross-Situational Word Learning: The Inverse Effect of Initial Accuracy

Intuitively, the accuracy of initial word-referent mappings should be positively correlated with the outcome of learning. Yet recent evidence suggests an inverse effect of initial accuracy in adults, whereby greater accuracy of initial mappings is associated with poorer outcomes in a cross-situational learning task. Here, we examine the impact of initial accuracy on 4-year-olds, 10-year-olds, and adults. For half of the participants most word-referent mappings were initially correct and for the other half most mappings were initially incorrect. Initial accuracy was positively related to learning outcomes in 4-year-olds, had no effect on 10-year-olds' learning, and was inversely related to learning outcomes in adults. Examination of item learning patterns revealed item interdependence for adults and 4-year-olds but not 10-year-olds. These findings point to a qualitative change in language learning processes over development.