The central concept of group-dynamics theory is cohesion, the attractiveness of the group to its members. As emphasized by TMT, cohesion is increased by the degree to which group consensus offers an antidote to uncertainty about issues of meaning and value. Cohesion is also increased by more mundane membership rewards, such as congeniality, status, and accomplishment of group goals.

High cohesion leads to strong pressures for uniformity on issues relevant to the group. This is basically a homeostatic prediction, in which differences of opinion that would get in the way of a social-reality consensus or pursuit of group goals must be controlled if members are to experience the rewards that attract them to the group. For group members, higher cohesion thus leads to greater acceptance of group norms, more rejection of deviates, and greater respect for and obedience to group leaders.

Although developed in studies of small face-to-face groups (primary groups), the predictions of group-dynamics theory can be scaled up to apply as well to larger collectivities, such as ethnic and national groups, that are so large that most members cannot be known personally (secondary groups). Identification with secondary groups is equivalent to cohesion in primary groups, and the consequences of primary-group cohesion can be predicted as well from identification with secondary groups. More identification should lead to greater acceptance of ethnic or national group norms, more rejection of those who deviate from these norms, and more respect for ethnic or national leaders.

The power of the group and the consequences of cohesion are explicated in some of the classic experiments in social psychology. In Solomon Asch's experiments on conformity, 75% of college students denied the evidence of their own eyes to give an incorrect judgment of line length when seven other students (confederates of the experimenter) unanimously gave the incorrect judgment. This power was increased by greater uncertainty (more difficult line discriminations) and decreased by any break in the unanimity of the majority (if even one confederate gave the objectively correct judgment). If the subjects could make their judgments privately rather than aloud, conformity was cut by two thirds.

One clear implication of these results is that group influence depends partly on group power to reward conformers and punish deviates; when the group could not hear the subject's judgment, conformity was decreased. The conformity remaining with private judgment shows a different kind of group influence, influence based on subjects accepting the judgments of others as valid information about reality. Group power to define reality is even stronger on issues of value, where there is no source of certainty except group consensus.

Both kinds of group power contribute to killing in intergroup conflict. Killers are controlled by the rewards and punishments of their group, and by their acceptance of group norms and the social reality defined by group consensus. In time of war, every state depends on coercion to make men fight: prison or death for refusing conscription, prison or death for desertion, prison or death for disobeying an order. Terrorist killers are probably less controlled by coercion than by the social-reality power of their group, inasmuch as terrorist groups only wish they had the reward and punishment powers of the state.

Even for soldiers, however, the controlling group norms tend to be more the values of the combat group than the values of the state. Research with American soldiers in particular has shown that, in the stress of combat, most soldiers fight less for cause or country or hatred of the enemy than for their buddies. The half dozen or dozen men who share the loneliness of the battlefield are closer than brothers; they fight because to do less is to endanger the group on which they are totally dependent. One of the great lessons of social psychology is that group power is maximized when group members have no other group to turn to. In combat groups as in terrorist groups, the individual's social world has contracted to just the few around him.

A similar account has been offered for genocidal killing. Christopher Browning describes how middle-aged German men in uniform came to participate in killing Jews. The Reserve Police were sent to Poland, separated from family, friends, and previous occupations in a foreign land where their only home was their unit. Their officers had orders to kill Jews, but, at least initially, did not threaten much coercion against men who could not or would not. In this situation, it is not individual motives of anti-semitism that explain the killing. Browning points instead to the cohesion of "ordinary men," for whom the best reason to kill Jews was that those who did less put more burden on their fellows.

Browning puts considerable emphasis also on desensitization and routinization of killing in explaining how men slowly escalated their participation in killing. This is the psychology of commitment, much studied in research on dissonance theory. In its modern version, dissonance is a theory of rationalization in which individuals sucked into stupid or sleazy behavior will change their opinions to justify and make sense of their behavior. Probably the paradigm case of this psychology is another classic study, Milgrams's research on obedience.

Milgram showed that the majority of normal individuals will give a supposed "learner" increasing levels of shock, up to a maximum 450-volt shock labeled "XXX DANGER STRONG SHOCK." Part of the power of this paradigm is the slow, graded nature of the shocks, which begin at only 15 volts and increase 15 volts with every mistake the "learner" makes. So close is the grading of shock levels that, at each level, to recognize something wrong with giving the next level must imply something wrong with the level already administered. Slow escalation of hurting others is a slippery slope in which each act of aggression becomes a reason for more aggression.

Taken together, group dynamics and the psychology of escalating commitment go a long way toward explaining how normal people can do awful things. Throw in the reward and punishment power of the state, a power that needs move only a small number of people to do the dirty work against a target class or race, and even genocide begins to be comprehensible.

Clark McCauley is Professor of Psychology at Bryn Mawr College and Co-Director of the Solomon Asch Center for the Study of Ethnopolitical Conflict at the University of Pennsylvania. He is an HFG grantee.

Suggested Reading

Averill, J. R. 1982. Anger and Aggression: An Essay on Emotion. New York: Springer.

Berkowitz, L. 1989. Frustration-aggression hypothesis: Examination and reformulation. Psychological Bulletin 106: 59-73.

Browning, C. R. 1992. Ordinary Men: Reserve Police Battalion 101 and the Final Solution in Poland. New York: HarperCollins.

Duckitt, J. 1989. Authoritarianism and group identification: A new view of an old construct. Political Psychology 10: 63-84.

Dodge, K. A. 1991. The structure and function of reactive and proactive aggression. In D. J. Pepler and K. H. Rubin (eds.) The Development and Treatment of Childhood Aggression. Hillsdale: Erlbaum.

Holmes, R. 1985. Acts of War: The Behavior of Men in Battle. New York: Free Press.

Kinder, D. R. 1998. Opinion and action in the realm of politics. In D. T. Gilbert, S. T. Fiske, and G. Lindzey (eds.) Handbook of Social Psychology, vol. 2. New York: McGraw-Hill.

McCauley, C. (ed.) 1991. Terrorism Research and Public Policy. London: Cass.

Pyszczynski, T., J. Greenberg, and S. Solomon. 1997. Why do we need what we need? A terror management perspective on the roots of human social motivation. Psychological Inquiry 8: 1-20.

Rummel, R. J. 1996. Death by Government. New Brunswick, N.J.: Transaction Publishers.

Smith, D. N. 1998. The psychocultural roots of genocide: Legitimacy and crisis in Rwanda. American Psychologist 53: 743-753.

Williamson, S., R. D. Hare, and S. Wong. 1987. Violence: Criminal psychopaths and their victims. Canadian Journal of Behavioral Science 19: 454-462.

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