Understanding other people's actions: intention and attention.

This study investigated the extent to which observation of an action performed by a human actor or a robotic arm may kinematically prime the performance of an observer subsequently required to perform a similar action. In Experiment 1, an actor reached for a target presented in isolation or flanked by a distractor object. Subsequently, an observer was required to perform a similar action toward the target object, but always in the absence of the distractor. The kinematics of both the human actor and the observer were affected by the presence of the distractor. Unexpectedly, similar effects were found in the observer's kinematics during the trials in which the actor was seated in front of the observer but no action was demonstrated (catch trials). Results from 4 subsequent experiments suggest that the motor intentions of the actor can be inferred by monitoring his or her gaze. To support this conclusion, results are discussed in terms of recent work spanning many disciplines involved in combining gaze direction and body movements.