Bilingualism and Memory Processing During Infancy and Early Childhood

Abstract

In 2011, approximately 60.6 million people in the U.S. above the age of 5 spoke a language other than English at home (Ryan, 2013). By 2018, this number increased to 67.3 million (U.S. Census Bureau, 2018). Despite this growth, bilingualism continues to be at the center of significant debates in the U.S. and around the globe. In the scientific field, most of the studies on bilingualism and cognition among children focus primarily on those above the age of three. This dissertation examined the relationship between variations in language exposure and cognition during infancy and early childhood, focusing primarily on verbal and non-verbal processes of memory.Chapter 2 analyzed differences in word learning skills after using the mutual exclusivity (ME) principle followed by a 5-minute delay to test for word retention. Despite both language groups using ME, monolinguals were more likely to remember the novel words after a delay than bilinguals. Following prior studies with infants suggesting that there might be other changes in cognitive skills outside of the verbal domain, we implemented three studies measuring non-verbal memory skills by assessing memory in the presence of interference (Chapter 3), across haptic-visual modalities (Chapter 4), and across perceptually different stimuli (Chapter 5). Chapter 3 established a new retroactive interference paradigm, but children’s performance did not differ as a function of language experience. Chapter 4 analyzed whether 18-month-olds’ abilities to transfer across modalities (haptic-visual) were related to differences in language exposure. Bilinguals and not monolinguals showed a novelty bias in the intra-modal trials but a familiarity bias for the cross-modal trials. Finally, we expanded the infant literature measuring generalization skills to an older population–preschoolers (Chapter 5). Despite the findings of 6- to 24-month-old bilinguals outperforming their monolingual peers, this advantage may reach a plateau by age 3. Overall, the findings from this dissertation add to the limited literature exploring the role of language exposure variations and memory processing skills during infancy and early childhood. As this population continues to grow worldwide, it is essential for cognitive and developmental researchers to examine the mechanisms behind these processing differences, especially with a younger population.