Prevalence of Autistic-Like Traits in General Population Bilingual and Monolingual Samples and Their Effect on Cognition and Metaphor Processing/Interpretation
Research on bilingualism has shown some advantages in Theory of Mind, in executive functions, and in specific areas of pragmatics. On the other hand, the same areas are often impaired in children with autism spectrum disorders (ASD). Hence, studying bilingualism and ASD symptomatology offers an avenue for investigating the interaction between contrasting cognitive profiles and their potential effects on pragmatic language development. Nevertheless, recent work has shown cultural bias in the ASD diagnosis. As bilinguals are often raised biculturally, acknowledging autistic traits in this population might be affected by the cultural bias. Therefore, to avoid such bias, this thesis takes a novel approach by investigating the prevalence of autistic-like traits (ALTs) in a general sample of bilingual and monolingual children (study 1). The thesis further investigates the effect of ALTs on cognition (study 2), and on metaphor processing and interpretation (study 3) in both bilinguals and monolinguals. The first study explored the distribution of ALTs in a general population sample of bilingual (n = 164) and monolingual (n = 230) children (age range: 5-12 years) based in the United Kingdom. The study found that age and structural language skills predicted 52% of variance in ALTs among bilinguals, while sex and structural language accounted for 29% of ALTs variance among monolinguals. Overall, bilingualism explained no variance in the ALTs. The second study investigated executive functions and Theory of Mind in 44 bilinguals (25 with low ALTs and 19 with high ALTs) and 50 monolinguals (28 with low ALTs and 22 with high ALTs), a subsample from study 1. Depending on the factors considered in the analyses, the study offers evidence for bilingual advantage, for monolingual advantage, and for no difference in cognitive performance between language and ALTs groups. The third study focused on metaphor processing and interpretation in the same sample as in study 2. On the processing task, true literal and false literal statements required less time to process than high familiarity metaphors. Furthermore, structural language skills significantly predicted processing speed. Once background factors were considered, children with low ALTs took longer to process metaphoric and literal phrases than children with high ALTs. The study found that higher age, socioeconomic status, and expressive vocabulary improve metaphor interpretation. Additionally, girls outperformed boys. Finally, language status and ALTs level had no effect on metaphor interpretation, indicating that background factors and core language skills (such as expressive vocabulary) determine metaphor understanding.