In this study, the Ajzen and Fishbein model, developed from their theory of reasoned action, was applied to the investigation of factors influencing adolescent health behaviour. This model proposes that intentions (by extension, behaviour) are explained by a weighted
combination of evaluated beliefs about that behaviour (i.e. attitudes) and motivation to comply with the wishes of significant referents concerning that behaviour (i.e. perceived social pressures).
Recent innovations in Health Education in schools seem implicitly to be based on this rationale. They seek to establish beliefs leading to good health behaviour and to develop in pupils the confidence to act in accordance with these beliefs in the face of possible contrary social pressures.
Questionnaires for measuring adolescents' intentions, beliefs and perceptions of social pressures concerning drinking alcohol, smoking cigarettes, keeping fit and diet were developed through a series of pilot trials, adapting the approaches suggested by Ajzen and Fishbein and subsequent workers. The reliability of these measures was shown to be satisfactory. Face and content validity were ensured during development: convergent and discriminant validity were evident, post hoc. The criterion-related validities of the scales were established, demonstrating the internal and external validity of the model itself.
A representative sample of pupils aged 11 to 18 years, from Berkshire secondary schools, completed these questionnaires. The amount of variance in intentions explained by the
weighted combination of the variance in beliefs and social pressures was statistically significant for all the topics and similar in magnitude to that frequently reported in
attitude-behaviour studies with adolescents. It was lower, however, than that reported by researchers using the Ajzen and Fishbein model with adults. Reasons for this short-fall
are considered: the unsuitability of the model for use with adolescents; the incorporation of constant and random error in the data; and the use of short scales.
Finally, the implications of the results for Health Education programmes are considered
