When adults and babies interact, they will often mimic each other’s expressions and emotions. This is sometimes referred to as behavioral synchrony. New research now suggests that in addition to behavioral synchrony, adults and infants may be able to synchronize their brain waves.
In the first experiment, 8 month old infants were shown videos of a female experimenter (not the mother) singing nursery rhymes. In these videos, the adult would either face and look at the camera directly (direct gaze), turn at an angle and look away from the camera (indirect gaze), or turn at an angle but maintain eye contact with the camera (direct-oblique gaze). The adults had their brain activity measured with an EEG when the videos were recorded. When the infants watched the video, researchers measured the infants’ brain activity with an EEG. The researchers also observed the infants’ vocalizations and interactions with the onscreen adult. They found stronger synchronization of brain waves between the infants and adults when there was eye contact, both in the direct and the direct-oblique conditions. There was no difference in duration or frequency of vocalization from the infant in response to the videos.
The researchers then repeated the experiment, but instead of a video, an adult sat in front of the infant and sang the nursery rhymes, again with the three different degrees of eye contact. Again, there was stronger synchronization with direct and direct-oblique gaze, but this time it appeared that not only were the infant’s brain waves becoming more synchronized with the adult, but the adult brain waves were also influenced by the infant. With the live interaction, infants also vocalized more frequently when there was direct eye contact, suggesting perhaps an intention to communicate. The amount of infant vocalization also predicted the degree to which the infant influenced the adult’s brain activity.
So what does this all mean? In adults, brain synchrony is believed to reflect attachment and social connectedness as well as social engagement. Thus it is likely that brain synchrony between adults and infants may also indicate social bonding. Direct eye contact perhaps engages infants and may provide important social cues for babies learning to interact with the world around them. In Dr. Leong’s study, the adult singing the nursery rhymes was a stranger, and still the babies engaged and synchronized with the adult. Based on studies in adults, one could expect even greater synchrony between babies and their caregivers. Recently Dr. Laura Cirelli presented work where mothers sang soothing or playful versions of songs to infants. In that study, the mothers and their babies’ behavioral responses were synchronized: when mothers sang songs in a soothing, calming manner, both infants and mothers showed lower stress responses. When mothers sang in a more playful, quicker manner, babies seemed more attentive and had more positive responses. Although Dr. Cirelli did not measure the brain waves, perhaps the brain synchrony underlies the behavioral changes she observed in her study. Together these studies highlight the importance of engaging in direct eye contact with infants and suggests a role for song and music in influencing behavior and mood.