12- to 14-month-olds expect unconstrained agents to act efficiently: Event-related potential (ERP) evidence from the head-touch paradigm.

Behavioral research has shown that 12- but not 9-month-olds imitate an unusual and inefficient action (turning on a lamp with one's forehead) more when the model's hands are free. Rational-imitation accounts suggest that infants evaluate actions based on the rationality principle, that is, they expect people to choose efficient means to achieve a goal. Accordingly, infants' expectations should be violated when observing inefficient actions....