INTRODUCTION Bay of Pigs and Cuban missile crisis decisions and results are detailed as introduction to group decision making.

Definitions: What Is a Group?

• A group is two or more people who are interacting with each other and are interdependent in the sense that to fulfill their needs and goals, they must rely on each other.

A. Why Do People Join Groups?

• Baumeister and Leary (1995) argue that people join groups because in our evolutionary past, there was a substantial survival advantage to establishing bonds with other people. Consequently the need to belong may be innate and is present in all societies.

• Groups have many benefits, including providing information, helping us define our identity, and establishing social norms for behavior.

B. The Composition and Functions of Groups

• Most social groups range in size from two to six members.

• Members of a group tend to be alike in terms of age, sex, beliefs, and opinions. This is both because people are attracted to similar others and because groups operate in ways that encourage similarity among members.

1. Social Norms

• Groups have social norms about which behaviors are acceptable, and the consequences of violating these are pressure to conform and ultimately rejection.

2. Social Roles

• Groups also often have well-defined roles, or shared expectations in a group about how particular people are supposed to behave. Roles facilitate social interaction.

• Roles also may have a cost. First, adopting a role can lead people to temporarily lose their personal identities. For example, Zimbardo and his colleagues set up a mock prison in the basement of the Stanford psychology department. They selected normal, healthy young men and randomly assigned them to be prisoners or guards. Many of the guards became aggressive and the prisoners passive and even severely anxious and