Recent neurophysiological studies have shown that several human brain regions involved in executing actions are activated by merely observing such actions via a human, and not by a mechanical hand. At a behavioral level, observing a human’s movements, but not those of a robot, significantly interferes with ongoing executed movements. However, it is unclear whether the biological tuning in the observation/execution matching system are functional during infancy. The present study examines whether a human’s actions, and not a mechanical action, influence infants’ execution of the same actions due to the observation/execution matching system. Twelve-month-old infants were given a searching task. In the tasks, infants observed an object hidden at location A, after which either a human hand (human condition) or a mechanical one (mechanical condition) searched the object correctly. Next, the object was hidden at location B and infants were allowed to search the object. We examined whether infants searched the object at location B correctly. The results revealed that infants in the human condition were more likely to search location A than those in the mechanical condition. Moreover, the results suggested that infants’ searching behaviors were affected by their observations of the same actions by a human, but not a mechanical hand. Thus, it may be concluded that the observation/execution matching system may be biologically tuned during infancy. 1. Introduction It has been proposed that actions are intrinsically linked to perception, and that imagining, observing, or in any way representing an action, excites the motor programs used to execute such actions. This proposal is originally derived from James’ ideomotor theory [1] and recently developed by Prinz’s common coding framework [2]. According to this framework, the representation of a perceived action involves simulative production of that action on the part of the observer. This covert motor activation results in the observation of an action facilitating its execution. Neurophysiological studies have supported the common coding framework by showing that several brain regions (e.g., the primary motor cortex) involved in executing actions are activated by the mere observation of such actions, through what is known as the mirror neuron in animals [3, 4] and the mirror neuron system in human [5, 6]. Importantly, the mirror neuron system can respond only to biological actions [7]. On the behavioral level, the biological tuning leads to the fact that observing a human’s arm movements, but not those of a robot,
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