We describe two series of experiments which examined whether and how young infants recognize causality in object motion and in human actions. The first series demonstrated using launching events featuring objects and people, that 8- but not -month-old infants appreciate that physical contact is necessary to set inanimate objects into motion but not to set people into motion. Eight-month-old infants appear to appreciate that people interact at a distance through some means of communication. The second series demonstrated that, when they see a stationary ball half-hidden by an occluder starting to move, 10-month-old infants infer the presence of the hidden agent that caused the ball to move. However, they do not infer the presence of the agent when a person replaced the ball. These findings suggest that infants differentiate between causes of object motion and those of human actions.

Key words; causal reasoning, cognitive development, habituation method, infants, naive physics