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The role of prosody during language acquisition and language processing: are prosodic cues used during lexical segmentation and syntactic analysis of spoken sentences?

Final Activity Report Summary - PROSODY LANGUAGE (The role of prosody during language acquisition and language processing: are prosodic cues used during lexical segmentation ... of spoken sentences?)

The main objective of this project was to investigate language processing in adults as well as language acquisition, in the area of lexical segmentation as well as syntactic analysis of spoken sentences. Initially, we proposed to evaluate the role of prosodic cues, since this source of information is directly available in the speech signal and thus could be useful, very early on; even in the first steps of language acquisition (especially as phrasal prosody is much exaggerated in child-directed speech). Moreover, prosodic boundaries always correspond to word boundaries but also to syntactic boundaries, so they can be useful in both lexical segmentation and syntactic parsing for both populations (adults and infants).

The first part of the project concerned the role of prosodic cues in lexical segmentation: we found that French-speaking adults were able to infer a word boundary when they heard a prosodic boundary. Interestingly, they were able to use intermediate prosodic boundaries (phonological phrase boundary cues) as well as more minor prosodic boundaries (prosodic word boundary cues) to segment spoken sentences correctly, even if the latter are less salient and less acoustically marked. Our results also support the view that phrasal prosody seems to influence the lexical segmentation processes in a gradual way (and argue against a threshold model). The more a prosodic boundary is marked, the more the listener supposes the presence of a word boundary.

The second part of the project dealt with the syntactic analysis of spoken sentences. We decided to investigate the role of another source of information, function words (that is articles, pronouns, auxiliaries, prepositions...) in the syntactic analysis of spoken sentences (more precisely in syntactic categorisation). As we proposed in our model of syntactic acquisition at the end of my doctoral thesis (see Christophe, Millotte, Bernal & Lidz, Language and Speech, 2008), these function words are very important since young infants could use them in order to infer the syntactic category of content words (by using the fact that nouns tend to co-occur with articles, whereas verbs tend to appear with pronouns or auxiliaries) and then in order to infer the meaning of word (by using the fact that nouns tend to denote objects whereas verbs tend to correspond to actions). Thus, one important pre-requisite for this model is that young infants know, very early on, what kind of function words is associated with what kind of syntactic category. We showed that this ability was present in the second year of life: for instance, 18 month-olds know that a noun has to be preceded by an article and not by a pronoun, whereas this is the reverse for verbs. Moreover, we showed that adults were also able to use function words, as well as more complex and larger syntactic context, in order to predict the syntactic category of upcoming words before identifying them (which allows them to speed up their lexical access and reduce ambiguities).

Finally, after having studied the acquisition of syntactic categories, we extended the syntactic part of this project to the question of the acquisition of word order. We showed that infants, as young as 20 months of age, possess an abstract representation of the word order of their language. They know that French language is a Subject-Verb-Object language, and are able to use this knowledge in order to infer the meaning of sentences.