Measuring Early Word Exposure in Infants: A Brief Parent-Report Survey Captures Individual Language Input and Predicts Vocabulary Outcomes

Individual differences in early language input are rampant but hard to quantify without resource-intensive naturalistic recordings, posing a challenge for testing links between individual experience and facets of language development like vocabulary growth. We tested whether a quick parent survey on infants’ exposure to common nouns could reliably predict nouns’ frequency in home-recordings (testing its validity) and children’s own vocabulary (testing input-learning links). In Study 1 (n=44; 95% White, 5% mixed-race) we gathered monthly home recordings and exposure surveys every two months from 8-18mo. Parent reported exposure to each noun (16/timepoint, 5-point scale) was compared to the noun’s relative frequency in infants' home-recordings, and to comprehension and production of each noun via parent vocabulary survey (CDI). Reported exposure significantly predicted noun frequency in home recordings. It also predicted both reported noun comprehension and production, even after accounting for age. Results from an age- and gender-matched cross-sectional sample (Study 2, n=264, 78% White, 11% mixed-race, 11% other) with the same vocabulary and exposure surveys were consistent, supporting generalizability. These findings suggest a brief word-exposure survey can reliably estimate individualized word input and knowledge, at least for highly common nouns. This method complements naturalistic recordings and corpus-based norms by capturing individual variation and enabling more scalable research across linguistic and sociocultural contexts.