Seeing vs. believing: Is believing sufficient to activate the processes of response co-representation?

It has been suggested that the observation of another person's action affects the behavior of the observer because the observation of action leads to the excitation of similar response codes in the observer. It is unknown, however, if one must witness the action or if it is sufficient for one to believe that the other agent is responding for response co-representation to occur. To this end, participants in the present study performed a joint spatial-compatibility task with a confederate when: (1) the confederate sat beside the participant; and, (2) the confederate left the room and told the participant that they would continue to perform their component of the task on a networked computer in another room. Even though participants believed that the confederate performed the task in another room, joint spatial-compatibility was only observed when the confederate was present. These results reveal that the actions of another person may only be represented by the observer when the observer is able to witness a portion of the action.