Growth of verbal short-term memory of nonwords varying in phonotactic probability: A longitudinal study with monolingual and bilingual children

This study investigates the hypothesis that verbal short-term memory growth in young children can be explained by increases in long-term linguistic knowledge. To this aim, we compare children's recall of nonwords varying in phonotactic probability. If our assumption holds, there should be growth in recall of high-probability nonwords, but no or less growth in recall of low-probability nonwords. Monolingual and bilingual children are compared to see if bilingual children who have less phonotactic knowledge of the target language (Dutch) show different growth patterns than their monolingual peers. Participants were 72 monolingual Dutch children and 69 bilingual Turkish-Dutch children with Dutch as their non-dominant language. Children were assessed at four, five and six years of age. At all ages, they completed serial nonword recall tasks containing Dutch-based high- and low-probability nonwords. They also performed a series of control measures, including a Dutch receptive vocabulary task. Latent Growth Modeling was used to model the data. A model with clear improvement in children's recall of high-probability nonwords, but no improvement in recall of low-probability nonwords in both groups, and equal gains of recall of high-probability nonwords in the two groups, gave good fit to the data. These results indicate that (i) verbal short-term memory growth can be explained by increases in long-term phonotactic knowledge and (ii) bilingual children with lower levels of phonotactic knowledge in the target language benefit from such knowledge to the same degree as monolingual children.