Theory of Planned Behaviour and Health Behaviour

Introduction to the Theory of Planned BehaviourPage 169

The Theory of Planned Behaviour (TPB) is an extension of the Theory of Reasoned Action (TRA), designed to predict volitional human behaviour. It posits that behaviour is a function of behavioural intentions and perceived behavioural control (PBC), with intentions being shaped by attitudes, subjective norms, and PBC.

Structure and Determinants of the ModelPage 171

The model operates on the premise that attitudes, subjective norms, and perceptions of control determine intentions. These components are, in turn, underpinned by behavioural beliefs, normative beliefs, and control beliefs. The TPB improves upon the TRA by acknowledging that internal and external barriers to behaviour are often perceived rather than absolute.

Meta-analytic Research FindingsPage 175

Meta-analytic reviews consistently show that the TPB explains a significant portion of variance in both intentions (40-50%) and behaviour (21-36%). Research across various health domains—such as physical activity, drug use, and sexual behaviour—validates the model as a robust framework, though the predictive power varies depending on the specific behaviour and population.

Key Issues and Model DevelopmentsPage 178

Critical discussions revolve around the role of affect, the importance of descriptive versus injunctive norms, and the distinction between perceived self-efficacy and controllability within the PBC construct. Additionally, there is interest in incorporating auxiliary predictors like anticipated regret and moral norms to improve the model's accuracy.

Operationalization and Intervention ApplicationsPage 194

Effective application of the TPB requires adhering to the principle of compatibility (matching the specificity of action, target, context, and time). While the TPB is useful for identifying cognitive targets for intervention, its effectiveness in actually changing behaviour remains a subject of ongoing research, highlighting a need for better intervention design and rigorous experimental testing.