Objective likeness of acts and the mental satisfaction found in being in conformity with others are baptized by the name imitation. This social fact is then taken for a psychological force, which produced the likeness. A considerable portion of what is called imitation is simply the fact that persons being alike in structure respond in the same way to like stimuli. Quite independently of imitation, men on being insulted get angry and attack the insulter. This statement may be met by citing the undoubted fact that response to an insult takes place in different ways in groups having different customs. In one group, it may be met by recourse to fisticuffs, in another by a challenge to a duel, in a third by an exhibition of contemptuous disregard. This happens, so it is said, because the model set for imitation is different. But there is no need to appeal to imitation. The mere fact that customs are different means that the actual stimuli to behavior are different. Conscious instruction plays a part; prior approvals and disapprovals have a large influence. Still more effective is the fact that unless an individual acts in the way current in his group, he is literally out of it. He can associate with others on intimate and equal terms only by behaving in the way in which they behave. The pressure that comes from the fact that one is let into the group action by acting in one way and shut out by acting in another way is unremitting. What is called the effect of imitation is mainly the product of conscious instruction and of the selective influence exercised by the unconscious confirmations and ratifications of those with whom one associates.