Human adults have a tendency to spontaneously and unconsciously copy or ‘mimic’ others’ behaviours, including their postures, gestures, facial expressions, and emotions. This mimicry plays an important role in social interaction. For example, it has been shown to increase liking between strangers, and makes our interactions more smooth and enjoyable. However, little is known about when and how mimicry develops in humans. It is believed that some form of mimicry starts early in infancy, with new-borns mimicking their parents’ facial actions; however these findings are controversial. What is clear is that mimicry increases with age, and that by around 3 years of age, children seem to show the kind of spontaneous mimicry that we see in adults. To help address the gaps of knowledge in this field, researchers at Birkbeck’s Centre for Brain Development and Cognition (CBCD) are investigating how mimicry develops from infancy to toddlerhood using electromyography (EMG) and fNIRS.
The CBCD has been testing a cohort of sixty infants at six month intervals, from 4 months until 3 years of age, acquiring both EMG and fNIRS data. The EMG gives an objective and sensitive measure of facial muscle movements during mimicry, whilst the fNIRS data can image brain activation. The brain’s mirror neuron system has been suggested as being involved in mimicry, so the team has focussed on investigating brain regions that cover 1) areas that support mimicry (i.e. the superior temporal sulcus (STS) and inferior frontal gyrus (IFG)), and 2) areas that modulate mimicry (i.e. the medial prefrontal cortex (mPFC) and temporo-parietal junction (TPJ)). By using fNIRS to look at brain activation, the CBCD team can image awake infants and collect data that is both robust to movement and has better spatial resolution than electroencephalography (EEG) or magnetoencephalography (MEG).
In the youngest cohort (4 months), CBCD assessed whether infants tendency to mimic is modulated by eye contact. Infants observed videos with models performing facial actions accompanied by direct or averted gaze. The EMG results showed an interaction between gaze direction and muscle activity, demonstrating that infants had a greater tendency to mimic facial actions accompanied by direct gaze. The fNIRS data showed greater brain activation over the left STS areas when infants observed facial actions accompanied by direct gaze. While at this visit the EMG and fNIRS data were acquired in separate sessions, from the next visit (at 11 months) onwards the EMG sensors were integrated into the fNIRS hat design allowing the researchers to measure mimicry and brain responses simultaneously. Using this EMG + fNIRS method the CBCD will continue to assess mimicry responses and the underlying neural mechanisms in this cohort as these infants age. Investigating how developmental factors such as sensorimotor experience, infants’ growing social cognitive abilities, and increasing brain connectivity influence the development and modulation of mimicry. Thus, we can expect more fNIRS results in the years to come with new and interesting cognitive paradigms.
For more information about this project please contact Carina de Klerk (firstname.lastname@example.org). The CBCD is always looking for more participants so if you live in or around London and are interested in participating in their studies with your child, visit the CBCD website and sign up online.