Infants' lexical comprehension and lexical anticipation abilities are closely linked in early language development.

Theories across cognitive domains propose that anticipating upcoming sensory input supports information processing. In line with this view, prior findings indicate that adults and children anticipate upcoming words during real-time language processing, via such processes as prediction and priming. However, it is unclear if anticipatory processes are strictly an outcome of prior language development or are more entwined with language learning and development. We operationalized this theoretical question as whether developmental emergence of comprehension of lexical items occurs before or concurrently with the anticipation of these lexical items. To this end, we tested infants of ages 12, 15, 18, and 24 months (N = 67) on their abilities to comprehend and anticipate familiar nouns. In an eye-tracking task, infants viewed pairs of images and heard sentences with either informative words (e.g., eat) that allowed them to anticipate an upcoming noun (e.g., cookie), or uninformative words (e.g., see). Findings indicated that infants' comprehension and anticipation abilities are closely linked over developmental time and within individuals. Importantly, we do not find evidence for lexical comprehension in the absence of lexical anticipation. Thus, anticipatory processes are present early in infants' second year, suggesting they are a part of language development rather than solely an outcome of it.