'Acting in' is defined as not telling a life story to the group verbally, but reenacting significant situations in the session. This serves as resistance which the leader counters by analyzing the group's reaction to it. To understand the origin of 'acting in' behavior, the leader must fortify the patient's ego, develop his coöperation, and show the patient the inappropriateness of his behavior. In a group this is difficult because the members involuntarily incite each other to 'acting in' responses often difficult to interpret.