A fNIRS investigation on non-adjacent linguistic regularities across development.

Infants have the ability to learn from their environment. The processes that underlie how they learn are still debated. Some authors suggest that learning is supported by the extraction of patterns or rules from a single stimulus; those rules will later underlie categorization. Consequently, infants will be able to generalize an abstract structure to any stimuli belonging to the given category. This ability to extract rules or patterns is believed to be shared across different domains, although robust evidence is limited to the linguistic field. In this thesis, we want to investigate rule extraction in a sample of 6-month-old infants, as well as an adult sample (mean age = 23 years). Based on the previous literature (Gervain et al., 2012), newborns are able to discriminate between trisyllabic words based on their grammatical structure. Indeed, the brain response to words with an AAB or ABB structure (i.e., the two adjacent syllables are identical) was significantly different from the response to ABC words (i.e., all syllables differ from each other). Nonetheless, they failed to distinguish between ABA and ABC words (Gervain et al., 2008). The lack of ability to distinguish non-adjacent repetitions in the newborn population pushed our investigation. Here, we want to observe if an older sample of infants shows different neural responses to words containing non-adjacent repetition, compared to unstructured words (ABA vs ABC). The aim is to assess a putative developmental trajectory, where the ability to distinguish between identity and non-identity is computed by the newborn locally- i.e., only between adjacent syllables- and by the infant globally-i.e., including the entire word into the computation process. The adult sample will instead provide information about how the computational process could change throughout development, once the individual has been exposed to a rich linguistic environment.