Neonatal imitation predicts infant rhesus macaque (Macaca mulatta) social and anxiety-related behaviours at one year.

Stefano S K Kaburu,Annika Paukner,Stephen J Suomi,Elizabeth A Simpson,Pier F Ferrari

doi:10.1038/srep34997

Abstract

The identification of early markers that predict the development of specific social trajectories is critical to understand the developmental and neurobiological underpinnings of healthy social development. We investigated, in infant rhesus macaques (Macaca mulatta), whether newborns’ capacity to imitate facial gestures is a valid predictive marker for the emergence of social competencies later in development, at one year of age. Here we first assessed whether infant macaques (N = 126) imitate lipsmacking gestures (a macaque affiliative expression) performed by a human experimenter in their first week of life. We then collected data on infants’ social interactions (aggression, grooming, and play) and self-scratching (a proxy indicator of anxiety) at 11–14 months when infants were transferred into a new enclosure with a large social group. Our results show that neonatal imitators exhibit more dominant behaviours, are less anxious, and, for males only, spend more time in play at one year old. These findings suggest that neonatal imitation may be an early predictor of infant sociality and may help identify infants at risk of neurodevelopmental social deficits.

Highlights

Who are imitators at 2–3 days and 3 weeks old show lower rates of gaze aversion at 3 months old when interacting with their mothers[4]
Whether neonatal imitation is the expression of a general behavioural response that is contingent with the context and the stage of development, or whether it represents a basic biological predisposition that could be considered as a trait with clear connections with other traits
We assessed neonatal imitation in the first week of life on 126 newborn rhesus macaques, and infants were classified as either lipsmacking (LPS) imitators or non-imitators

Summary

Introduction

Who are imitators at 2–3 days and 3 weeks old show lower rates of gaze aversion at 3 months old when interacting with their mothers[4]. In the first week of life, imitators, compared to non-imitators, appear to (1) be more attentive during neonatal imitation assessments[17], (2) better remember social partners[18], and (3) exhibit superior delayed imitation[19], suggesting imitators may be more socially advanced than non-imitators It remains largely unclear, whether neonatal imitation is the expression of a general behavioural response that is contingent with the context and the stage of development, or whether it represents a basic biological predisposition that could be considered as a trait with clear connections with other traits. This critical information is missing from the current literature To fill this gap, we took advantage of the described interindividual variability in neonatal imitative responses and examined whether infant rhesus macaques who imitate facial gestures in their first week of life displayed greater social skills than non-imitators at one year old. (3) display a greater frequency of dominant behaviours measured as aggression directed to peers as dominant behaviour is commonly linked to an individual’s ability to attain higher ranks[29]; and (4) show lower rates of self-scratching, which, in NHP, is considered a proxy indicator of anxiety[30]

Methods

Results

Conclusion