A comparison of leading theories for the prediction of goal-directed behaviours

A number of attitude theories have been proposed recently to explain behaviours subject to thwarting by internal and external impediments. The present research compares the theory of reasoned action, the theory of planned behaviour, a portion of the theory of self-regulation, and the theory of trying and performs tests of their ability to predict two actions relatively low in perceived behavioural control: exercising and dieting. Respondents were 142 students who participated in a two-wave survey over a two-week period. The results indicate that, while attitudes significantly predicted intentions in ail theories, subjective norms lead to intentions only under the theory of trying. Further, the effects of past behaviour were not channelled entirely through attitudes, subjective norms, or perceived behavioural control but rather had direct effects on intentions and subsequent behaviour. When past behaviour was taken into account, it was found that the performance of the target acts were not functions of intentions, and perceived behavioural control failed to predict either intentions or behaviour. Desires had strong direct effects on intentions and mediated most of the impact of attitudes. A number of theoretical implications of the findings are discussed.