Chapter 5 discusses research and theory on individual differences (the person who is in the situation being studied by social psychologists), especially identity, gender, and dispositions (or personality traits). The goal of the chapter is to identify some of the personal characteristics that have been studied most often by social psychologists to understand social behaviour. Many measures of individual differences have been developed and validated over the last 20 or 30 years, so social psychologists today can find measures to assess a wide variety of dispositions. This availability of diverse measures has resulted in more and more social psychologists using personality or identity measures in their studies even if their primary interest is not individual differences. Thus, personality psychology has become increasingly integrated into experimental social psychology. The close relationship between social and personality psychology is illustrated by the premier journal in social psychology, which is the journal of personality and social psychology.