Eye contact modulates facial mimicry in 4-month-old infants: An EMG and fNIRS study

Carina C.J.M De Klerk,Antonia F.De C Hamilton,Victoria Southgate

doi:10.1016/j.cortex.2018.05.002

Carina C.J.M De Klerk, Antonia F.De C Hamilton + Show 1 more

Open Access

https://doi.org/10.1016/j.cortex.2018.05.002

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Abstract

Mimicry, the tendency to spontaneously and unconsciously copy others' behaviour, plays an important role in social interactions. It facilitates rapport between strangers, and is flexibly modulated by social signals, such as eye contact. However, little is known about the development of this phenomenon in infancy, and it is unknown whether mimicry is modulated by social signals from early in life. Here we addressed this question by presenting 4-month-old infants with videos of models performing facial actions (e.g., mouth opening, eyebrow raising) and hand actions (e.g., hand opening and closing, finger actions) accompanied by direct or averted gaze, while we measured their facial and hand muscle responses using electromyography to obtain an index of mimicry (Experiment 1). In Experiment 2 the infants observed the same stimuli while we used functional near-infrared spectroscopy to investigate the brain regions involved in modulating mimicry by eye contact. We found that 4-month-olds only showed evidence of mimicry when they observed facial actions accompanied by direct gaze. Experiment 2 suggests that this selective facial mimicry may have been associated with activation over posterior superior temporal sulcus. These findings provide the first demonstration of modulation of mimicry by social signals in young human infants, and suggest that mimicry plays an important role in social interactions from early in life.

Highlights

Humans' tendency to copy others' actions plays an important role in cultural learning (e.g., Legare & Nielsen, 2015; Tomasello, Kruger, & Ratner, 1993) and serves a highly social function (Over & Carpenter, 2013)
We found greater mimicry of facial actions accompanied by direct compared to averted gaze, and this effect seemed strongest for the observation of eyebrow actions (See supplementary materials for additional analyses on the z-scored EMG activity per muscle region)
Hereafter we investigated the relationship between those channels that were sensitive to gaze direction and the facial mimicry effects measured in Experiment 1, to identify the brain regions that may play a role in modulating facial mimicry by eye contact

Summary

Introduction

Humans' tendency to copy others' actions plays an important role in cultural learning (e.g., Legare & Nielsen, 2015; Tomasello, Kruger, & Ratner, 1993) and serves a highly social function (Over & Carpenter, 2013). Contrary to imitation, which is usually intentional and objector effect-directed, mimicry is thought to occur outside of cortex 1 0 6 ( 2 0 1 8 ) 9 3 e1 0 3 conscious awareness and is most common for non-object directed actions such as postures, gestures, and facial expressions (Chartrand & Bargh, 1999). This mimicry behaviour has been shown to play an important role in communication and affiliation (Chartrand & Lakin, 2013). Based on these findings it has been suggested that mimicry evolved to serve as ‘social glue’, binding individuals together and creating harmonious relationships, thereby facilitating survival (Lakin, Jefferis, Cheng, & Chartrand, 2003)

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