Typological linguistic diversity and L1 lexical knowledge and processing in kindergartners: behavioral and neural signatures

The paper aims at establishing whether relative differences and similarities between languages multilingual children are exposed to contribute to the development of their cognition and brain. Our goal was to investigate the effects of typological linguistic diversity on first language (L1) lexical knowledge and processing in kindergartners and establish its behavioral and neural signatures. We analyzed 162 data points collected from 5-6-year-old kinder-gartners with various language backgrounds on a monolingual-to-quintilingual continuum. Detailed parental questionnaires and in-person interviews were used to calculate the length of cumulative exposure to any language each child in the sample came into contact with. We then gathered information on the relative linguistic distances between each child’s languages, based on languages’ lexicons. Two behavioral outcome variables were used in the study: (1) receptive and (2) expressive L1, English vocabulary; the neuroimaging data consisted of fMRI sequences collected during an English Audito-ry Word-Form Match Task. To deal with variable language backgrounds of our participants, we leveraged computational tools from information tech-nology – Shannon’s (1948) entropy, and the study of ecological diversity – Rao’s (1982) quadratic entropy index of diversity, thus offering a novel, multi-dimensional quantification of language exposure in multilinguals. Our results show that typological linguistic diversity can be related to expressive but not receptive L1 vocabulary scores. On neural level, it relates to brain activation patters in (among others) the PGa area in the bilateral IPL, a brain region that previous studies repeatedly associated with multilingual experience, but never with typological linguistic diversity. With this study, we propose an ecologically valid way of describing the continuum of multilingual language experience, an approach rarely followed but highly called for in the multilingual literature. We furthermore provide evidence for both the cognition and the brain of multilingual kindergartners to be related to the typological linguistic diversity of their environment.