Groups are the setting for most social activities. All but an occasional recluse or exile belong to groups, and those who insist on living their lives apart from others, refusing to join any groups, are considered curiosities, eccentrics, or even mentally unsettled (Storr, 1988). Nearly all human societies are organized around small groups, such as families, clans, communities, gangs, religious denominations, and tribes, and the influence of these groups on individual members is considerable. Virtually all social activities-working, learning, worshiping, relaxing, playing, socializing, chatting in cyberspace communities, and even sleeping-occur in groups rather than in isolation from others.Groups exert a ubiquitous, unrelenting influence over their members, shaping both their psychological adjustment and their dysfunction. Those who study mental health-clinical psychologists, counseling psychologists, community psychologists, health psychologists, social workers, and psychiatrists-have long recognized the relationship between groups and 339