According to some views of cognitive growth, the development of working memory capacity can account for increases in the complexity of cognition. It has been difficult to ascertain, though, that there actually is developmental growth in capacity that cannot be attributed to other developing factors. Here we assess the role of item familiarity. We…

The lexicon of 6-month-olds is comprised of names and body part words. Unlike names, body part words do not often occur in isolation in the input. This presents a puzzle: How have infants been able to pull out these words from the continuous stream of speech at such a young age? We hypothesize that caregivers' interactions directed at and on…

Human children possess the ability to approximate numerical quantity nonverbally from a young age. Over the course of early childhood, children develop increasingly precise representations of numerical values, including a symbolic number system that allows them to conceive of numerical information as Arabic numerals or number words. Functional…

Young children engage in essentialist reasoning about natural kinds, believing that many traits are innately determined. This study investigated whether personal experience with second language acquisition could alter children's essentialist biases. In a switched-at-birth paradigm, 5- and 6-year-old monolingual and simultaneous bilingual…

How objects are held determines how they are seen, and may thereby play an important developmental role in building visual object representations. Previous research suggests that toddlers, like adults, show themselves a disproportionate number of planar object views--that is, views in which the objects' axes of elongation are perpendicular or…

To what extent do toddlers have shared vocabularies? We examined CDI data collected from 14,607 infants and toddlers in five countries and measured the amount of variability between individual lexicons during development for both comprehension and production. Early lexicons are highly overlapping. However, beyond 100 words, toddlers share more…

We tested the hypothesis that developmental precursors to aggression are apparent in infancy. Up to three informants rated 301 firstborn infants for early signs of anger, hitting and biting; 279 (93%) were assessed again as toddlers. Informants' ratings were validated by direct observation at both ages. The precursor behaviours were…

The aim of this study was to examine the association of breastfeeding practices with the growth trajectories of children's cognitive development. We used data from the Child Development Supplement (CDS) of the Panel Study of Income Dynamics (PSID) with variables on presence and duration of breastfeeding and standardized test scores obtained…

How does the brain's response to speech change over the first months of life? Although behavioral findings indicate that neonates' listening biases are sharpened over the first months of life, with a species-specific preference for speech emerging by 3 months, the neural substrates underlying this developmental change are unknown. We…

We tested the hypothesis that dopamine D1 and D2 receptor gene (DRD1 and DRD2, respectively) polymorphisms and the development of working memory skills can interact to influence symptom change over 10 years in children with attention-deficit/hyperactivity disorder (ADHD). Specifically, we examined whether improvements in working memory maintenance…

We show that children in the Tsimane', a farming-foraging group in the Bolivian rain-forest, learn number words along a similar developmental trajectory to children from industrialized countries. Tsimane' children successively acquire the first three or four number words before fully learning how counting works. However, their learning…

The study assessed the relations among acuity of the inherent approximate number system (ANS), performance on measures of symbolic quantitative knowledge, and mathematics achievement for a sample of 138 (64 boys) preschoolers. The Weber fraction (a measure of ANS acuity) and associated task accuracy were significantly correlated with mathematics…

Learning of the mathematical number line has been hypothesized to be dependent on an inherent sense of approximate quantity. Children's number line placements are predicted to conform to the underlying properties of this system; specifically, placements are exaggerated for small numerals and compressed for larger ones. Alternative hypotheses…

Being able to see a talking face confers a considerable advantage for speech perception in adulthood. However, behavioural data currently suggest that children fail to make full use of these available visual speech cues until age 8 or 9. This is particularly surprising given the potential utility of multiple informational cues during language…

Children learn the structure of the music of their culture similarly to how they learn the language to which they are exposed in their daily environment. Furthermore, as with language, children acquire this musical knowledge without formal instruction. Two critical aspects of musical pitch structure in Western tonal music are key membership…