Experience Shapes Early Noun Comprehension from 8-18 Months: The Roles of Word Frequency and Referent Familiarity

We investigated how experience with particular nouns and referents influences infant word comprehension by combining home recordings with in-lab eyetracking. In Study 1, infants (n=44) participated in a yearlong longitudinal study which included monthly home recordings (daylong audio and hourlong video, 6-17mo.) and hand-tailored eyetracking experiments (every two months, 8-18mo.). Word comprehension was operationalized as how much more infants looked at named images than distractors. Each session tested 16 words: 8 held constant across all infants at each timepoint ("generic" common nouns, e.g., "shoe"), and 8 hand-picked for each session from each child's recent home recordings. Of the hand-picked items, half appeared as images familiar to children from home (e.g., their own ball); the other half and all generic items appeared as prototypical child-friendly (but not individually-tailored) images. Results showed expected improvements with age, and an effect of word frequency (particularly at 12 and 14mo. timepoints) but not referent familiarity. In Study 2 (n=247), cross-sectional controls completed the same eyetracking experiments (i.e., those hand-tailored for Study 1 children) as a stronger test of the roles of frequency and referent familiarity. Here, we did find an effect of referent familiarity. Study 2 infants understood words less well than those in Study 1, particularly when tested with images of referents selected from Study 1 children's homes. Together, these findings highlight the role of experience in shaping early noun comprehension and suggest that once infants understand words, they readily generalize them to new instances beyond those they are familiar with.