The link between non-human primate vocalizations and cognition is not constrained by maturation alone: Evidence from healthy preterm infants

To acquire language, infants must not only identify the signals of their language(s), but also discover how these signals are connected to meaning. By 3 months of age, infants' native language, non-native languages, and vocalizations of non-human primates support infants' formation of object categories—a building block of cognition. But by 6 months, only the native language exerts this cognitive advantage. Prior work with preterm infants indicates that maturation constrains this developing link between the native language and cognition. Here, we assess whether maturation exerts similar constraints on the influence of non-human primate vocalizations on infant categorization. Cross-sectional growth curve analyses of new data from preterm infants and extant data from fullterm infants indicate that developmental tuning of this signal's influence on categorization is best predicted by infants' chronological age, and not gestational status. This evidence, together with prior work, suggests that as infants tune the initially broad set of signals that support early cognition, they are guided by two independent processes: maturation constrains the expression of a link between their native language and cognition, while the influence of non-linguistic signals are guided by other factors, such as postnatal age and experience.