Eight-month-old infants' behavioral responses to peers' emotions as related to the asymmetric frontal cortex activity.

Infants are sensitive to and converge emotionally with peers' distress. It is unclear whether these responses extend to positive affect and whether observing peer emotions motivates infants' behaviors. This study investigates 8-month-olds' asymmetric frontal EEG during peers' cry and laughter, and its relation to approach and withdrawal behaviors. Participants observed videos of infant crying or laughing during two separate sessions. Frontal EEG alpha power was recorded during the first, while infants' behaviors and emotional expressions were recorded during the second session. Facial and vocal expressions of affect suggest that infants converge emotionally with their peers' distress, and, to a certain extent, with their happiness. At group level, the crying peer elicited right lateralized frontal activity. However, those infants with reduced right and increased left frontal activity in this situation, were more likely to approach their peer. Overall, 8-month-olds did not show asymmetric frontal activity in response to peer laughter. But, those infants who tended to look longer at their happy peer were more likely to respond with left lateralized frontal activity. The link between variations in left frontal activity and simple approach behaviors indicates the presence of a motivational dimension to infants' responses to distressed peers.