The Effects of Social Identity and Perceived Autonomy Support on Health Behaviour Within the Theory of Planned Behaviour

The present study employed constructs from self-determination theory, social-identity theory, and the theory of planned behaviour to examine the combined effects that social identity and perceived autonomy support exerted on attitudes, intentions and health behaviour. A prospective design was employed measuring constructs from the theory of planned behaviour, group norms, group identification, and perceived autonomy support at baseline and physical activity behaviour 5 weeks later. Self-report questionnaires were administered to 231 pupils (male = 113, female = 118, M = 14.21 years, SD = .90). Hierarchical regression analysis demonstrated that group norms predicted participation in physical activities and attitudes, but only for participants who identified strongly with their group. Perceived autonomy support predicted attitudes, intentions and behaviour. The effects of perceived autonomy support and social-identity constructs were independent. It was concluded that both social identity and perceived autonomy support should be included in the theory of planned behaviour.