Experience Tunes the Link between Nonhuman Primate Vocalizations and Cognition: Evidence from Healthy Preterm Infants

• In Event: Poster Session 05
  In Poster Session: PS 05 Topic - Cognitive Processes

Abstract

To acquire language, infants must identify which signals carry relevant communicative cues and discover how these signals are linked to meaning. By 3 months of age, listening to language supports infants’ ability to form object categories, a building block of cognition (Ferry, Hespos, & Waxman, 2010). This link between human language and cognition emerges from a broad biological template that initially also includes the vocalizations of nonhuman primates (Ferry, Hespos, & Waxman, 2013). Within the first half year, the link to cognition rapidly narrows specifically to human language: by 6 months, nonhuman primate vocalizations no longer exert the advantageous effect for categorization that persists throughout the first year for language.

We hypothesize that two complementary, but independent processes are at play in refining the link between human language and cognition: (1) the strengthening and reinforcement of the link between linguistic signals and cognition and (2) the narrowing of this link to exclusively human language through the exclusion of other nonlinguistic signals. If these two processes are independent, then the influence of linguistic and nonlinguistic signals on infant categorization may be affected differently by developmental factors such as maturation and postnatal experience.

Evidence from preterm infants reveals that developmental changes in infants’ expression of the link between language and cognition is primarily dependent on their maturational age—not the duration of their postnatal experience (Perszyk, Ferguson, & Waxman, 2016). Although preterm infants have had a longer period of postnatal experience with language than fullterm infants of the same maturational age, this additional exposure does not confer an advantage in the developmental trajectory for expressing a link between language and cognition. Thus, for the first process—strengthening the link between language and cognition—maturation is key. Here, we ask whether the second process—narrowing this link to exclusively human language—is also driven by maturation, or whether postnatal experience influences this developmental change.

Healthy late preterm infants (born 33-37 weeks post conception; postnatal age 4-12 months; n=22; data collection still underway) participated in an object categorization task while listening to a nonlinguistic signal (nonhuman primate vocalizations; Eulemur macaco flavifrons) that supports fullterm infants’ object categorization at 3-4 months, but not at 6-12 months. Initial results indicate that the second process—developmental tuning of the link to cognition to only human language—unfolds in preterm infants on the same experiential timetable as fullterm infants, despite their pre-mature status. Preterm infants’ looking behavior was similar to fullterm infants at the same postnatal age (4mos & 6-12mos: p>0.05), with preterm infants expressing an initial novelty preference at 4 months (t(4)=2.899, p=0.044) which fades by 6 months (p>0.05).

This finding, in tandem with the previous report on preterm infants listening to language, suggests that two separate processes refine the link between human language and cognition. Infants’ expression of the link between language and cognition is primarily influenced by maturation, while the elimination of the advantageous effect that some nonlinguistic signals initially have on infant cognition is primarily driven by postnatal experience.

Authors

• Kali Woodruff Carr, Northwestern University
  Presenting Author

• Danielle Perszyk
  Non-Presenting Author

• Murielle Standley, Northwestern University
  Non-Presenting Author

• Sandra R Waxman, Northwestern University
  Non-Presenting Author