The present study investigates the contribution of 2 mechanisms to imitation in infancy. The principle of rational action suggests that infants normatively evaluate the efficiency of observed actions. In contrast, it has been proposed that motor resonance (i.e., the mapping of others' actions onto one's own motor repertoire) plays a central role in imitation. This study tested 14-month-old infants (n = 95) in 5 conditions and manipulated the extent to which the observed actions could be matched onto the infants' own motor repertoire as well as whether the observed behavior appeared to be efficient. The results suggest that motor resonance plays a more central role in imitation in infancy than does a rational evaluation of the observed action.