By utilizing reinforcing and punishing light cues the verbal output and leadership status of Target Ss in a four-person group was manipulated. There were three conditions: Control (no light cues used); Agree, where Non-Target Ss were reinforced for agreeing with the Target, and punished for all other verbalizations; and Disagree, where Non-Target Ss were reinforced for disagreeing with the Target and punished for all other verbalizations. From social exchange theory it was predicted that both experimental groups would show significant increases on the dependent measures over trials and in comparison with a control group, but the Disagree group would not show the same effect on the leadership rankings. In general, the results supported the notion that one leadership function is the maximization of the rewards/costs ratio, and the group will rank members in the order of their ability to fulfill this function. (Author)