Introduction: social problems, human cognition, and behaviourMany, if not most, societal problems are rooted in behaviour or human cognitions. For example, integration problems may result from conflicts between groups and the inherent human tendency to favour one's own group, and traffic accidents are to a large extent caused by unsafe driving styles and the unrealistic perception that one is a better driver than most others. Moreover, health problems are related to unhealthy eating habits and a sense of not being able to control one's appetite, and environmental problems result in part from growing consumption levels and a tendency to prioritize one's immediate self interests above collective interests. Consequently, solutions and prevention of such problems require changes in attitudes, values, norms, behaviour, and lifestyles (Zimbardo, 2002). Social psychologists can play an important role in this respect, by applying their theories, methods, and interventions to these problems.Social psychology is the scientific field that seeks to understand the nature and causes of human behaviour and thought in social situations, and the motivations, cognitions, and emotions related to such behaviours. This includes behaviour and thoughts related to helping, attraction, conflict, prejudice, self-esteem, group processes, and social exclusion (Baron and Byrne, 2004). Box 1.1 illustrates how social psychologists may help resolve social problems by encouraging behaviour changes, and highlights several issues that enhance the social utility of applied social psychological studies. First, in order to design effective solutions for social problems, we have to understand which behaviour causes the given problem. Applied scientists can best focus on behaviour that significantly contributes to a social problem and where interventions would have the most impact in resolving these problems. In our example, speeding by moped riders was studied because moped riders are relatively often involved in traffic accidents, while, in turn, these traffic accidents appeared to be strongly related to speeding. Second, it is important to examine which factors influence the particular behaviour. Behaviour-change programmes will be more effective when they target important antecedents of behaviour. Thus, we need to understand which factors cause behaviour. Third, it is important to understand which intervention techniques are available to change behaviour, taking into account which behavioural antecedents are typically targeted by various intervention techniques.