When asked to introduce ourselves a key aspect of our self-description will be our occupation. Certainly if we fail to identify what we do it is very likely that we will be asked. Even if we are unemployed, the very absence of employment will be part of our identity. Those who have studied identity have long realized that human identity is largely tied up in the groups we inhabit, our social identity. We carry a representation of our social world in our minds and use this to negotiate our everyday world. For many, a large percentage of this is the world of work. Although we are quite often unaware of it, the groups in our minds determine much of our behaviour and experience. Have you ever been in a meeting and been surprised by the behaviour of colleagues who you thought you knew? Have you ever wondered at committee decisions which seem unfair or irrational to you? People in groups behave differently to when they are alone, and indeed may behave very differently from one group to another. The thesis of thisbook is that work behaviour cannot be understood by focusing on individuals. Real explanations are to be found at the levels of groups or organizations and the way in which those groups and organizations are incorporated in the individual mind. Individuals, Groups and Organisationswill be of interest to students of social psychology, organisational psychology and business and management.