Do bilingual and monolingual children differ? : measuring and comparing attentional control skills in the verbal and non-verbal domains

The aim of the current master’s thesis was to investigate 1) whether bilingual and monolingual children display differences in behavioural measures of attentional control in the verbal and non-verbal domains and 2) whether attentional control performance in children correlates across domains. The present study therefore explored the impact of being bilingual from birth on the cognitive skills (specifically attentional control) and lexical retrieval proficiency of early-school-aged children in Greater Sydney, Australia. Participants included monolingual (N=17) and bilingual (N=17) Australian born children who were matched in age, sex and parental education. Bilingual participants were exposed to two languages from birth and were highly proficient in both their languages. Chapter 1 introduces the thesis, including the literature review and general design of the study. Chapter 2 presents the study of the verbal domain in terms of children’s lexical performance. In this Chapter, performance in the letter and category verbal fluency task (VFT) (partially in Pino Escobar et al., 2016) are analysed and compared between language groups. Chapter 3 investigates the cognitive non-verbal domain under the Dimensional Card Change Sort (DCCS) and the Day-Night Stroop task (Day-Night). Afterwards, Chapter 4 investigates the relations between verbal and non-verbal tasks of attentional control in bilingual and monolingual children. Finally, Chapter 5 concludes the thesis with a General discussion. Results indicated better bilingual performance on the letter and category VFT but comparable performance between monolingual and bilingual groups on the DCCS and the Day-Night task. It was also found that performance in the letter VFT correlated with the DCCS while no relation between category VFT and the Day-Night task was found. Regression analyses, however, showed that while DCCS performance predicted only letter VFT; vocabulary proficiency (as measured by the Peabody Picture Vocabulary Test (PPVT)) predicted performance of both letter and category VFT. Results were explained in light of the characteristics of the participant samples. Firstly, bilingual and monolingual groups were strictly matched in age and gender, both groups exhibited similar parental education backgrounds and similar English receptive vocabulary proficiency. And secondly and more importantly, bilingual participants were highly proficient and productive in an additional language. It was therefore proposed that this last characteristic conferred bilinguals with additional attentional control to efficiently sort and retrieve words under different conditions. These results suggest that during complex lexical retrieval (i.e., letter VFT) seven to eightyear-old bilingual and monolingual children can recruit high order attentional control. In sum, our findings show that both vocabulary proficiency and general attentional control skills account for monolingual and bilingual children’s performance on complex verbal fluency tasks. Additionally, controlling for vocabulary proficiency has a determining factor when comparing monolingual and bilingual performance: high vocabulary proficiency in both languages likely underlies the unprecedented bilingual advantage shown in the present study.