Day by day, hour by hour: Naturalistic language input to infants.

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Measurements of infants' quotidian experiences provide critical information about early development. However, the role of sampling methods in providing these measurements is rarely examined. Here we directly compare language input from hour-long video-recordings and daylong audio-recordings within the same group of 44 infants at 6 and 7 months. We compared 12 measures of language quantity and lexical diversity, talker variability, utterance-type, and object presence, finding moderate correlations across recording-types. However, video-recordings generally featured far denser noun input across these measures compared to the daylong audio-recordings, more akin to 'peak' audio hours (though not as high in talkers and word-types). Although audio-recordings captured ~10 times more awake-time than videos, the noun input in them was only 2-4 times greater. Notably, whether we compared videos to daylong audio-recordings or peak audio times, videos featured relatively fewer declaratives and more questions; furthermore, the most common video-recorded nouns were less consistent across families than the top audio-recording nouns were. Thus, hour-long videos and daylong audio-recordings revealed fairly divergent pictures of the language infants hear and learn from in their daily lives. We suggest that short video-recordings provide a dense and somewhat different sample of infants' language experiences, rather than a typical one, and should be used cautiously for extrapolation about common words, talkers, utterance-types, and contexts at larger timescales. If theories of language development are to be held accountable to 'facts on the ground' from observational data, greater care is needed to unpack the ramifications of sampling methods of early language input.





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Bergelson, Elika, Andrei Amatuni, Shannon Dailey, Sharath Koorathota and Shaelise Tor (2019). Day by day, hour by hour: Naturalistic language input to infants. Developmental science, 22(1). p. e12715. 10.1111/desc.12715 Retrieved from

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Shannon Egan-Dailey

Postdoctoral Associate

Shannon is a Postdoctoral Associate in the Sanford School of Public Policy, working on Baby's First Years with Dr. Lisa Gennetian. Shannon's research examines children's language input and their developing language skills over time using various behavioral methods. She is interested in how children’s early language experience varies systematically between children and families (such as by child gender or family socioeconomic status) and how that affects children's language development. She has expertise investigating language development using experimental, observational, and longitudinal methods. On Baby's First Years, she is investigating the mechanisms of socioeconomic-based differences in children's language experiences and development.

Shannon completed her PhD in developmental psychology at Duke University in 2022, advised by Dr. Elika Bergelson. She received a BA in psychology with honors from the University of Pennsylvania in 2015.

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