Big Question 4
Variability in language processing and in language learning:
Why does the ability to learn language change with age? How can we characterise and map individual language skills in relation to the population distribution?
We aim to characterize variation in language processing and learning skills and to determine how these variations relate to variations in the underlying biology of individual participants. The project has two strands: Strand A focuses on language processing skills in young adults, and Strand B on language learning skills in children and adults. Strand A will develop a comprehensive battery of language tasks targeting sound, meaning, and grammatical processing of words and longer utterances during speaking and listening. In addition, we will select or develop tasks assessing general cognitive skills that are likely to affect performance in language tasks. After extensive piloting, a demographically representative group of 1000 young adults will be tested on the battery. DNA will be obtained from all participants and used for genome-wide genotyping. About a third of the sample will also participate in neuroimaging studies in order to map the variation in neurobiology across the population. Advanced statistical modelling will be used to derive underlying core dimensions of linguistic ability, to situate each participant in a multidimensional skill space that maps population variation, and determine the manner in which these skills map onto structure and function of underlying brain circuitry. Integrating our new sample with Nijmegen’s existing Brain Imaging Genetics cohorts, we will carry out focused investigations of genes and biological pathways that have been previously implicated in language ability, test how polygenic scores relate to performance on the task battery, and perform mediation analyses to bridge genes, brains and cognition.
Strand B uses variability in learning ability to investigate why second-language (L2) acquisition can become harder in adulthood. Do age-related differences in L2 learning reflect maturational changes in neural plasticity and in the schema-based mnemonic processes used for learning and consolidating linguistic knowledge and skills? We will examine age-related changes in the relative contributions of the medial temporal lobe and the medial prefrontal cortex and in the interactions between these pathways and the perisylvian language network. 360 children aged 8-17 and 360 adults from the Strand A sample will complete batteries of behavioural and neuroscientific tests on L2 learning. Analyses will seek to uncover associations between language-learning abilities and maturational changes in the brain and to characterize individual variability in these associations.