My social psychology journey began in 1968 when I went to Edinburgh University as an undergraduate. As some may remember, that year was also memorable for other reasons. It was the year that Martin Luther King, that great civil rights leader, was assassinated. It was the year that Enoch Powell, a Conservative British politician, made a hateful speech apocalyptically predicting that unchecked immigration would lead to civil unrest and bloodshed on the streets of Britain. It was the year when “les evénements” in Paris threatened to upset the established order in several European countries. And it was the year when invading Soviet tanks brought the nascent Prague Spring to a swift and brutal end in Czechoslovakia.

The question of which comparisons members of social groups make is a fascinating one, not least because a preference or aversion for certain types of comparisons will have a number of important implications. For example, comparison choices may determine whether people perceive existing discrimination, whether they feel deprived, and whether they are satisfied with their own or their group's outcomes. Comparison choices might also affect perceptions of entitlement and they might raise or lower people's aspirations. Not surprisingly, then, comparisons play a central role in several social psychological theories of intergroup relations, such as Social Identity Theory (Tajfel and Turner, 1986) and Relative Deprivation Theory (Runciman, 1966).

In this chapter, we will briefly review some predictions about comparison choices that can be derived from one of the most important theories of intergroup relations, namely Social Identity Theory (SIT). Then, we will discuss some other theories and research which suggest that some additional mechanisms are at play which are neglected in the original SIT conception. Synthesizing the insights from these two sections, the research questions can be summarized in four themes: the effect on comparison choices of (a) comparison motives, (b) status/deprivation relative to a target, (c) structural variables (stability, permeability, and legitimacy), and (d) identification. To address these four themes, we will review some empirical evidence we have obtained from three surveys among members of different ethnic groups and seven studies that used different methodologies and focussed on different intergroup contexts.

This chapter is concerned with the effects of intergroup similarity on intergroup attitudes and behaviour. Now similarity can, of course, take a number of forms but, for reasons which will become obvious as the chapter progresses, the discussion concentrates mainly on two. These are attitudinal similarity – that is, similarity between the values and ideologies prevalent in the groups in question, and status similarity – the proximity of groups on some dimension of value or prestige. As I shall show, the concept of similarity occupies a central position in several theories of social relations. Broadly speaking, these fall into two main camps. The first, and by far the predominant view, holds that similarity has attractive or convergent properties on intergroup relations. Thus, groups which are like one another are held to enjoy friendlier and more cooperative relations than those which differ. The second camp reaches quite the opposite conclusion and hypothesizes that groups which become too similar may look for ways to discriminate against each other. The purpose of this chapter is to examine these rival claims in the light of the available evidence.

The discussion proceeds more or less historically. It begins with three major theories dating from the beginnings of modern social psychology – frustration–aggression theory, social comparison theory, and balance theory – and goes on to describe some more recent work in the same mould. These theories collectively make up the first of the two camps – what might be called the similarity–attraction position.