Blog post written by Natalie H. Brito based on an article in the journal Bilingualism: Language and Cognition
Although the majority of multilingual children learn languages sequentially, typically learning their first language in the home and their second language from school, a number of children are exposed to two or even three languages in the home from birth. Studies have found differences between infants exposed to one language vs. two on tasks tapping memory flexibility – as early as 6-months of age (Brito & Barr, 2014). Memory flexibility is the ability to retrieve past memories despite changes in cues and context, and memory flexibility has been tested using the deferred imitation memory generalization task. In this task, the experimenter demonstrates a series of actions with a toy, then after a delay, the infant is given the opportunity to play with the toy and demonstrate the previously seen target actions Generally, infants are able to recall the target actions when the toy is the same from demonstration to test, but fail to do so when there are inconsistencies in shape, color, or object. The good news is that infants become better able to flexibly apply past memories as they grow older. For example, previous research demonstrated that monolingual 18-month-olds were unable to generalize across two puppets, a yellow duck and a black/white cow, but could do so 3 months later at 21-months of age. Using the same puppets, we found that bilingual, but not monolingual, infants were able to generalize at 18-months after a 30-minute delay (Brito & Barr, 2012).
In a recent study (Brito, Sebastián-Gallés, & Barr, 2015), we examined what factors may influence memory performance for bilingual infants. In the first experiment we examined the role of language similarity; bilingual 18-month-ols who heard to two similar languages (Spanish-Catalan) or two more different (English-Spanish) languages were tested on a memory generalization task and compared to monolingual 18-month-olds. In the second experiment we tested trilingual 18-month-olds exposed to a variety of languages and compared their performance to infants from the first experiment. Our results indicated that both bilingual groups (Spanish-Catalan & English Spanish) outperformed the monolingual groups, with no significant differences between the two bilingual groups. Interestingly, infants exposed to three languages from birth performed the same as the monolingual groups. For the trilinguals, it is possible that more experience processing the three languages is necessary and similarities between bilinguals and trilinguals may be more apparent later in life. These findings demonstrate early emerging differences in memory flexibility and contribute to our understanding of how early environmental variations shape the trajectory of memory development.