Infants can help and share in the second year of life. However, there is limited knowledge as to variability in these behaviors as a function of target (e.g., caregiver vs. unfamiliar adult) and the influence of caregiver support on infant prosocial behavior. Infants (N = 268, 124 female) at 1-2 years of age (M = 1.47, SD = 0.27) and again at 2-3…

As they develop into mature speakers of their native language, infants must not only learn words but also the sounds that make up those words. To do so, they must strike a balance between accepting speaker-dependent variation (e.g., mood, voice, accent) but appropriately rejecting variation when it (potentially) changes a word's meaning (e.g., cat…

This research investigates the development of constraints in word learning. Previous experiments have shown that as infants gain more knowledge of native language structure, they become more selective about the forms that they accept as labels. However, the developmental pattern exhibited depends greatly on the way that infants are introduced to…

Parents commonly vocalize to infants to mitigate their distress, especially when holding them is not possible. Here we examined the relative efficacy of parents' speech and singing (familiar and unfamiliar songs) in alleviating the distress of 8- and 10-month-old infants (n = 68 per age group). Parent-infant dyads participated in 3 trials of the…

Accurate perception of emotional (facial) expressions is an essential social skill. It is currently debated whether emotion categorization in infancy emerges in a "broad-to-narrow" pattern and the degree to which language influences this process. We used an habituation paradigm to explore (a) whether 14- and 18-month-old infants perceive…

Children who rapidly recognize and interpret familiar words typically have accelerated lexical growth, providing indirect evidence that lexical processing efficiency (LPE) is related to word-learning ability. Here we directly tested whether children with better LPE are better able to learn novel words. In Experiment 1, 17- and 30-month-olds were…

Previous research indicates that infant-directed speech (IDS) is usually slower than adult-directed speech (ADS) and mothers prefer placing a focused word in isolation or utterance-final position in (English) IDS, which may benefit word learning. This study investigated the speaking rate and word position of IDS in two typologically-distinct…

Previous event-related potential (ERP) work has indicated that the neural processing of action sequences develops with age. Although adults and 9-month-olds use a semantic processing system, perceiving actions activates attentional processes in 7-month-olds. However, presenting a sequence of action context, action execution and action conclusion…

This article investigates infant comprehension of filler-gap dependencies. Three experiments probe 15- and 20-month-olds' comprehension of two filler-gap dependencies: "wh"-questions and relative clauses. Experiment 1 shows that both age groups appear to comprehend "wh"-questions. Experiment 2 shows that only the younger…

Previous studies have shown that by 11 but not by 10 months infants recognize words that have become familiar from everyday life independently of the experimental setting. This study explored the ability of 10-, 11-, and 12- month-old infants to recognize familiar words in sentential context, without experimental training. The headturn preference…

This research examined whether infants tested longitudinally at 10, 14, and 16 months of age (N = 58) showed evidence of perceptual narrowing based on face gender (better discrimination of female than male faces) and whether changes in caregiving experience longitudinally predicted changes in infants' discrimination of male faces. To test face…

The present research investigated the role of familiarity and proximity in infants' comprehension of displaced speech. When 13-and 16-month-old infants heard a researcher talk about a familiar person immediately after she left the room, they showed comprehension of the name by looking, pointing, or searching for the person in question. The…

Although human infants demonstrate early competence to retain visual information, memory capacities during infancy remain largely undocumented. In three experiments, we used a Visual Paired Comparison (VPC) task to examine abilities to encode identity (Experiment 1) and spatial properties (Experiments 2a and 2b) of unfamiliar complex visual…

We assessed the eye-movements of 4-month-old infants (N = 38) as they visually inspected pairs of images of cats or dogs. In general, infants who had previous experience with pets exhibited more sophisticated inspection than did infants without pet experience, both directing more visual attention to the informative head regions of the animals,…

The speed of a moving object is a critical variable that factors into actions such as crossing a street and catching a ball. However, it is not clear when the ability to discriminate between different speeds develops. Here, we investigated speed discrimination in 6- and 10-month-old infants using a habituation paradigm showing infants events of a…