Blood donation and Ajzen's theory of planned behaviour: an examination of perceived behavioural control.

In spite of the success achieved by the theory of reasoned action, researchers continue to suggest that new components should be added to the original model. Indeed, Ajzen has himself acknowledged that some behaviours may be subject to control problems and thus proposed the theory of planned behaviour to handle behaviours of this kind. This study set out to explore the predictive superiority of the revised theory of planned behaviour by focusing on blood donation, a behavioural domain in which volitional control was thought to be incomplete. It was also the intention to explore the extent to which the belief-based measure of attitude exists as a multidimensional construct. An Ajzen & Fishbein type questionnaire was administered to 141 undergraduate students. Multiple regression analyses provided strong support for the theory of planned behaviour, suggesting that perception of control has an important impact on a person's behavioural motivation. Also, some support for a multidimensional representation of the belief-based measure of attitude was provided.