share first authorship. Elika Bergelson, Andrei Amatuni, and Shannon Dailey were in Brain and Cognitive Sciences at the University of Rochester during data collection. Authors have no conflicts of interest to declare.

Infants amass thousands of hours of experience with particular items, each of which is representative of a broader category that often shares perceptual features. Robust word comprehension requires generalizing known labels to new category members. While young infants have been found to look at common nouns when they are named aloud, the role of item familiarity has not been well-examined. This study compares 12-18-month-olds' word comprehension in the context of pairs of their own items (e.g. photos of their own shoe and ball) versus new tokens from the same category (e.g. a new shoe and ball). Our results replicate previous work showing that noun comprehension improves rapidly over the second year, while also suggesting that item familiarity appears to play a far smaller role in comprehension in this age-range. This in turn suggests that even before age two, ready generalization beyond particular experiences is an intrinsic component of lexical development.

Around their first birthdays, infants begin to point, walk, and talk. These abilities are appreciable both by researchers with strictly standardized criteria and caregivers with more relaxed notions of what each of these skills entails. Here we compare the onsets of these skills and links among them across two data collection methods: observation and parental report. We examine pointing, walking, and talking in a sample of 44 infants studied longitudinally from 6–18 months. In this sample, links between pointing and vocabulary were tighter than those between walking and vocabulary, supporting a unified socio-communicative growth account. Indeed, across several cross-sectional and longitudinal analyses, pointers had larger vocabularies than their non-pointing peers. In contrast to previous work, this did not hold for walkers’ vs. crawlers’ vocabularies in our sample. Comparing across data sources, we find that reported and observed estimates of the growing vocabulary and of age of walk onset were closely correlated, while agreement between parents and researchers on pointing onset and talking onset was weaker. Taken together, these results support a developmental account in which gesture and language are intertwined aspects of early communication and symbolic thinking, whereas the shift from crawling to walking appears indistinct from age in its relation with language. We conclude that pointing, walking, and talking are on similar timelines yet distinct from one another, and discuss methodological and theoretical implications in the context of early development.

Infants amass thousands of hours of experience with particular items, each of which is representative of a broader category that often shares perceptual features. Robust word comprehension requires generalizing known labels to new category members. While young infants have been found to look at common nouns when they are named aloud, the role of item familiarity has not been well-examined. This study compares 12-18-month-olds’ word comprehension in the context of pairs of their own items (e.g. photos of their own shoe and ball) versus new tokens from the same category (e.g. a new shoe and ball). Our results replicate previous work showing that noun comprehension improves rapidly over the second year, while also suggesting that item familiarity appears to play a far smaller role in comprehension in this age-range. This in turn suggests that even before age two, ready generalization beyond particular experiences is an intrinsic component of lexical development.

Infants amass thousands of hours of experience with particular items, each of which is representative of a broader category that often shares perceptual features. Robust word comprehension requires generalizing known labels to new category members. While young infants have been found to look at common nouns when they are named aloud, the role of item familiarity has not been well-examined. This study compares 12-18-month-olds’ word comprehension in the context of pairs of their own items (e.g. photos of their own shoe and ball) versus new tokens from the same category (e.g. a new shoe and ball). Our results replicate previous work showing that noun comprehension improves rapidly over the second year, while also suggesting that item familiarity appears to play a far smaller role in comprehension in this age-range. This in turn suggests that even before age two, ready generalization beyond particular experiences is an intrinsic component of lexical development.