The major health care challenge in the twenty-first century, as it was at the close of the twentieth century, will be motivating people to make changes in their own behaviour in ways that reduce the risk of health and medical problems and enhance health. These motivational efforts must consist not only of educating people about the positive and negative effects of various behaviours but also, and perhaps more importantly, persuading people that they indeed can change their behaviour and teaching them the skills for doing so. For this reason, understanding self-regulation – the capacity of people to think about the future, set goals, develop plans to attain these goals, and regulate their own behaviour based on these goals and plans – will be crucial to solving the health and medical problems of the twenty-first century (see ‘Health-related behaviours’).

Self-regulation consists of several key components, including setting goals, developing plans, monitoring progress towards goals and modifying one's plans and behaviours in reaction to perceived progress towards one's goals. At the heart of the ability to self-regulate is the ability to develop expectancies – to use past experience and knowledge to form beliefs about and predict future events (Olson et al., 1996). The expectancy construct is among the most thoroughly investigated constructs in psychology. Expectancies gained importance with the development of social learning theory, as originally developed by Rotter (1954) (see also Woodward, 1982).