From associative to controlled learning of non-adjacent dependencies - brain function and structure

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Infants are able to learn their native language spontaneously within just a few years, that is, they seem to be equipped with remarkable language learning abilities. Using event-related potentials (ERPs), Friederici, Müller & Oberecker (2011, PloS ONE) found that 4-month-old German infants discriminate grammatical from ungrammatical non-adjacent dependencies (NADs) after only brief exposure, while adults were not able to learn during passive listening, but only when they had to perform an explicit grammaticality judgment task. This indicates a developmental shift from infants’ effortless, associative learning of NADs to adults’ top-down/controlled learning. In adults, the prefrontal cortex might exhibit top-down control over the learning, by inhibiting associative bottom-up learning mechanisms and hence limiting the ability to learn NADs under passive listening. Our ERP and fNIRS data from the first funding period of CROSSING reveal NAD learning under passive listening for 24-month-olds in the linguistic domain (i.e., spoken non-native sentences) but not in the non-linguistic domain (i.e., tone sequences), while 36-months-olds did not show learning in either domain. Hence, the data suggest a domain-specific shift of associative learning mechanisms underlying NAD learning from 24 to 36 months of age. Extending this research, we aim to answer the following questions in the presented research proposal: (1) What are the essential features of the signal in the linguistic domain vs. the non-linguistic domain that promote 24-months-olds’ learning under passive listening in the former, but not the latter? (2) Which learning conditions need to be fulfilled to promote controlled and successful learning beyond the age of 3 years? (3) Are the supposed developmental changes in the learning mechanisms constrained by the maturation of the grey and white matter of the brain? Which structural and functional brain networks underlie the changes in learning NADs in 3- to 6-year-olds? (4) In addition, we will draw a more detailed picture of NAD learning in relation to the development of general cognitive competences in 2- to 6-year-old children.