The early development of human mirror mechanisms: evidence from electromyographic recordings at 3 and 6 months

In primates and adult humans direct understanding of others' action is provided by mirror mechanisms matching action observation and action execution (e.g. Casile, Caggiano & Ferrari, 2011). Despite the growing body of evidence detailing the existence of these mechanisms in the adult human brain, their origins and early development are largely unknown. In this study, for the first time, electromyographic (EMG) measures were used to shed light on the emergence of mirror motor mechanisms in infancy. EMG activity was recorded while 6- and 3-month-old infants watched two videos displaying an agent reaching for, grasping and bringing an object either to the mouth or to the head. Results indicate that the motor system of 6-month-olds, but not 3-month-olds, was recruited and selectively modulated during observation of the goal-directed actions, favoring the idea that mirror mechanisms driving action understanding gradually emerge during early development.