Moving beyond "nouns in the lab": Using naturalistic data to understand why infants' first words include uh-oh and hi

Abstract

Why do infants learn some words earlier than others? Primarily informed by lab-based studies of noun-to-object mapping, current theories of early word learning depend on stable visual referents and prioritize cues, such as concreteness and imageability, when predicting early acquisition. However, more abstract words, such as uh-oh and hi, are typically among the first to appear in infants’ vocabularies. We combined a behavioral experiment with naturalistic observational research to explore how infants learn and represent this understudied category of high-frequency, routine-based non-nouns, which we term ‘everyday words’. In Study 1, we found that conventional eye-tracking measures of comprehension were insufficient to capture 10- to 16-month-old infants’ emerging understanding of everyday words. In Study 2, we moved beyond the constraints of a lab setting and analyzed the scenes surrounding production of these words in a naturalistic video corpus. This ecologically motivated research revealed that everyday words rarely co-occurred with consistent visual referents, making early acquisition difficult to reconcile with dominant word learning theories. Our findings instead point to complex patterns in the types of situations surrounding production of everyday words that could contribute to their early learnability. By leveraging both experimental and observational methods, this investigation underscores the value of using naturalistic data to broaden theories of early word learning.