For the last 20 years, developmental psychologists have measured the variability in lexical development of infants and toddlers using the MacArthur-Bates Communicative Development Inventories (CDIs)--the most widely used parental report forms for assessing language and communication skills in infants and toddlers. We show that CDI reports can…

Theories of language acquisition have highlighted the importance of adult speakers as active participants in children's language learning. However, in many communities children are reported to be directly engaged by their caregivers only rarely (Lieven, 1994). This observation raises the possibility that these children learn language from…

Three experiments investigated the effect of an adult's social cues on 2- and 3-year-old children's ability to use a sign or symbol to locate a hidden object. Results showed that an adult's positive, engaging facial expression facilitated children's ability to identify the correct referent, particularly for 3-year-olds. A neutral facial expression…

Twelve-month-olds realize that when an agent cannot see an object, her incomplete perceptions still guide her goal-directed actions. What would happen if the agent had incomplete perceptions because she could see only one part of the object, for example one side of a screen? In the present research, 16-month-olds were first shown an agent who…

Why do people perseverate, repeating prior behaviours that are no longer appropriate? Many accounts point to isolated deficits in processes such as inhibition or attention. We instead posit a fundamental difference in rule representations: flexible switchers use active representations that rely on later-developing prefrontal cortical areas and are…

We compared working memory (WM) for the location of social versus non-social targets in infant siblings of children with Autism Spectrum Disorders (sibs-ASD, n = 25) and of typically developing children (sibs-TD, n = 30) at 6.5 and 9 months of age. There was a significant interaction of risk group and target type on WM, in which the sibs-ASD had…

This study explored the electrophysiology underlying intonational phrase processing at different stages of syntax acquisition. Developmental studies suggest that children's syntactic skills advance significantly between 2 and 3 years of age. Here, children of three age groups were tested on phrase-level prosodic processing before and after this…

Human toddlers learn about objects through second-by-second, minute-by-minute sensory-motor interactions. In an effort to understand how toddlers' bodily actions structure the visual learning environment, mini-video cameras were placed low on the foreheads of toddlers, and for comparison also on the foreheads of their parents, as they jointly…

Data from three experiments provide the first evidence that children, at least as young as age two, are vigilant of others' non-verbal cues to credibility, and flexibly use these cues to facilitate learning. Experiment 1 revealed that 2- and 3-year-olds prefer to learn about objects from someone who appears, through non-verbal cues, to be…

The aim of this study was to measure the pattern of hand preferences for pointing gestures as a function of object-manipulation handedness in 123 infants and toddlers (10-40 months). The results showed that not only right-handers but also left-handers and ambidextrous participants tended to use their right hand for pointing. There was a…

Two experiments demonstrate that 14- to 18-month-old toddlers can adaptively change how they categorize a set of objects within a single session, and that this ability is related to vocabulary size. In both experiments, toddlers were presented with a sequential touching task with objects that could be categorized either according to some…

Syntax allows human beings to build an infinite number of new sentences from a finite stock of words. Because toddlers typically utter only one or two words at a time, they have been thought to have no syntax. Using event-related potentials (ERPs), we demonstrated that 2-year-olds do compute syntactic structure when listening to spoken sentences.…

We examined gestural and verbal interactions in 226 mother-infant pairs from Mexican, Dominican, and African American backgrounds when infants were 14 months and 2 years of age, and related these interactions to infants' emerging skills. At both ages, dyads were video-recorded as they shared a wordless number book, a wordless emotion book, and…

In gender-marking languages, the gender of the noun determines the form of the preceding article. In this study, we examined whether French-learning toddlers use gender-marking information on determiners to recognize words. In a split-screen preferential looking experiment, 25-month-olds were presented with picture pairs that referred to nouns…

Both animals and human toddlers can find an object in a rectangular enclosure after they have been disoriented. They use geometric cues (relative lengths of walls) to discriminate among different corners (e.g. long wall to the left, short to the right). It has been claimed that this ability is "modular", i.e. exclusively geometric. The present…