The model
Intention is said to be shaped by three things: a person's attitude toward the behaviour, the subjective norm, or perceived social pressure, and perceived behavioural control, meaning how easy or difficult the behaviour seems. Perceived control can also predict behaviour directly when it reflects actual ability.
How well it predicts
Meta-analyses show that the model accounts for a substantial share of variation in intentions and a smaller share of variation in behaviour. It has been used across health, transport and environmental research, often to design questionnaires that identify which beliefs a campaign might target.
Criticisms
The main criticism is the gap between intention and action: many people who intend to act do not follow through. Critics have also pointed out that experimental tests of whether changing the model's components changes behaviour are less convincing than correlational results, and that it says little about habit and impulse.
Further reading
- Ajzen, I. (1991). The theory of planned behavior. Organizational Behavior and Human Decision Processes, 50, 179-211.
- Armitage, C. J., & Conner, M. (2001). Efficacy of the theory of planned behaviour: A meta-analytic review. British Journal of Social Psychology, 40, 471-499.
- Sniehotta, F. F., Presseau, J., & Araujo-Soares, V. (2014). Time to retire the theory of planned behaviour. Health Psychology Review, 8, 1-7.