Prosody enhances learning of statistical dependencies from continuous speech streams in adults

Foreign languages sound like seamless streams of speech sounds without pauses between words and phrases. This makes it challenging for the listener to discover the underlying structure of a new language. However, all spoken languages have a melody, and changes in pitch, syllable duration and stress can provide prosodic cues about word and phrase boundaries. It is currently underspecified how adults use prosodic cues to crack the structure of a new language. Here, we investigated how pitch patterns affect the ability to learn adjacent and nonadjacent statistical dependencies from novel, artificial speech streams. In a series of eight online experiments along two studies, we presented native Finnish speakers with short, two-minute speech streams with a hidden probabilistic structure that did or did not include prosodic pitch patterns. We measured learning outcomes using a forced choice recognition task along with confidence ratings. In Study 1, we found that learning adjacent dependencies was boosted with familiar-to-listener (i.e., typical for Finnish language) prosodic pitch patterns but not with unfamiliar-to-listener or random prosodic pitch patterns. In Study 2, we found that more complex nonadjacent dependencies were only learned with the presence of familiar-to-listener prosodic patterns. Intriguingly, prosodic patterns also enabled concurrent learning of multiple adjacent and nonadjacent dependencies in speech. Moreover, they enhanced participants' confidence in remembering adjacent, but not nonadjacent, dependencies. Together, the results suggest that adults use language-background-dependent prosodic patterns to acquire novel linguistic knowledge from speech streams in a fast and efficient manner. The findings support the idea that prosody has an important role in language learning, making the underlying statistical structure of spoken languages more accessible and learnable for listeners.