Self-identity and the theory of planned behaviour: a useful addition or an unhelpful artifice?

Among the variables proposed as useful additions to the structure of the theory of planned behavior (Ajzen, 1991), there is evidence for the predictive usefulness of a measure of self-identity. In the study reported here, members of the general population in the United Kingdom (n = 235) completed a questionnaire addressing the consumption of a diet low in animal fats. The questionnaire was structured in terms of the TPB and contained additional variables that previous research has indicated to be useful predictors of intentions and behavior. A multiple regression of intentions (R-2 = .80) showed self-identification as a health-conscious consumer to have a predictive effect independent of the effects of these other variables. This effect was also found in replication studies.