Changes in selective attention to articulating mouth across infancy: Sex differences and associations with language outcomes.

Infants' attention to the mouth is thought to support language acquisition, yet this relation has been scantly tested longitudinally. This study assessed attention to the mouth and the eyes at 5.5 (n = 91; Polish, 49% females) and 11 months, between time-point changes and their associations with language development in infancy (11 months) and toddlerhood (24 months). Sex differences were also explored. Results showed an age-related increase in looking to the mouth, and the magnitude of this change was associated with productive language, but only in toddlerhood. By contrast, looking to the eyes did not change and its duration at 5.5 months correlated with language development at 2 years. Exploratory analyses showed that in females but not males, reduced mouth-looking was related to better language outcomes in toddlerhood. Thus, looking to the mouth in infancy likely plays a long-term role in language acquisition and is potentially modulated by participant sex.