ABSTRACT
Whether bilingual children outperform monolingual children on visuospatial and verbal working memory tests was investigated. In addition, relations among bilingual proficiency, language use at home, and working memory were explored. The bilingual Turkish-Dutch children (n=68) in this study were raised in families with lower socioeconomic status (SES) and had smaller Dutch vocabularies than Dutch monolingual controls (n=52). Having these characteristics, they are part of an under-researched bilingual population. It was found that the bilingual Turkish-Dutch children showed cognitive gains in visuospatial and verbal working memory tests when SES and vocabulary were controlled, in particular on tests that require processing and not merely storage. These findings converge with recent studies that have revealed bilingual cognitive advantages beyond inhibition, and they support the hypothesis that experience with dual language management influences the central executive control system that regulates processing across a wide range of task demands. Furthermore, the results show that bilingual cognitive advantages are found in socioeconomically disadvantaged bilingual populations and suggest that benefits to executive control are moderated by bilingual proficiency.
Subject(s)
Memory, Short-Term , Multilingualism , Child, Preschool , Female , Humans , Male , Neuropsychological Tests , Psychology, Child , Socioeconomic Factors , VocabularyABSTRACT
The current study examined to what extent information in long-term memory concerning the distribution of phoneme clusters in a language, so-called long-term phonotactic knowledge, increased the capacity of verbal short-term memory in young language learners and, through increased verbal short-term memory capacity, supported these children's first and second language vocabulary acquisition. Participants were 67 monolingual Dutch and 60 bilingual Turkish-Dutch 4-year-olds. The superior recall of nonwords with high phonotactic probability compared with nonwords with low phonotactic probability indicated that phonotactic knowledge was supportive for verbal short-term recall in both languages. The extent of this support depended on prior experiences with the language: The Turkish-Dutch children showed a greater phonotactic probability effect in their native language Turkish compared with their Dutch peers, and the monolingual Dutch children outperformed the bilingual Turkish-Dutch children in their native language Dutch. Regression analyses showed that phonotactic knowledge, indicated by the difference in recall of nonwords with high versus low phonotactic probability, was an important predictor of vocabulary in both languages.
Subject(s)
Mental Recall , Multilingualism , Phonetics , Semantics , Verbal Learning , Vocabulary , Child, Preschool , Female , Humans , Male , Memory, Short-Term , Probability , Recognition, Psychology , Retention, PsychologyABSTRACT
BACKGROUND: Brain serotonin function is thought to promote sleep regulation and cognitive processes, whereas sleep abnormalities and subsequent behavioral decline are often attributed to deficient brain serotonin activity. Brain uptake of the serotonin precursor tryptophan is dependent on nutrients that influence the availability of tryptophan via a change in the ratio of plasma tryptophan to the sum of the other large neutral amino acids (Trp:LNAA). OBJECTIVE: We tested whether evening consumption of alpha-lactalbumin protein with an enriched tryptophan content of 4.8 g/100 g increases plasma Trp:LNAA and improves alertness and performance on the morning after sleep, particularly in subjects with sleep complaints. DESIGN: Healthy subjects with (n = 14) or without (n = 14) mild sleep complaints participated in a double-blind, placebo-controlled study. The subjects slept at the laboratory for 2 separate nights so that morning performance could be evaluated after an evening diet containing either tryptophan-rich alpha-lactalbumin or tryptophan-low placebo protein. Evening dietary changes in plasma Trp:LNAA were measured. Behavioral (reaction time and errors) and brain measures of attention were recorded during a continuous performance task. RESULTS: Evening alpha-lactalbumin intake caused a 130% increase in Trp:LNAA before bedtime (P = 0.0001) and modestly but significantly reduced sleepiness (P = 0.013) and improved brain-sustained attention processes (P = 0.002) the following morning. Only in poor sleepers was this accompanied by improved behavioral performance (P = 0.05). CONCLUSION: Evening dietary increases in plasma tryptophan availability for uptake into the brain enhance sustained alertness early in the morning after an overnight sleep, most likely because of improved sleep.
