Rapid facial reactions in response to happy and angry expressions in 7‐month‐old infants

Humans rapidly and spontaneously activate muscles in the face when viewing emotional facial expressions in others. These rapid facial reactions (RFRs) are thought to reflect low-level, bottom-up processes, and are theorized to assist an observer to experience and share the affect of another individual. It has been assumed that RFRs are present from birth; however to date, no study has investigated this response in children younger than 3 years of age. In the present study, we used facial electromyography (EMG) to measure corrugator supercilii (brow) and zygomaticus major (cheek) muscle activity in 7-month-old infants while they viewed happy and angry facial expressions. The results showed that 7-month olds exhibited greater zygomaticus activity in response to happy expressions than angry expressions, however, we found no evidence of differential corrugator muscle activity.