This chapter reviews relevant personality and social identity theorising and research, and outlines their potential points of integration in attempting to explain and predict the performance of small student groups. It illustrates the integration of both perspectives with a simulation analysis based on data from real small student groups that worked on a project over a period of one academic year. Theorists and researchers have criticised the trait perspective for being unable to explain why people often behave inconsistently across situations and for being dismissive of how and why people are affected by the external environment and social contexts. The group personality and social identity approaches offer very distinct explanations of what factors contribute to the success of small student groups. From both empirical and theoretical standpoints, the personality trait and social identity approaches can be considered complementary as long as they are not radically postulated.