Predicting fruit consumption: A multi-group application of the Theory of Planned Behavior

Abstract The main aim of the study was to test a two-wave longitudinal prediction model for the consumption of at least three portions of fruit per day, that was grounded on the Theory of Planned Behaviour (TPB; Ajzen, 1991), extended with measures of past behaviour and self-identity as a healthy eater. Self-identity is defined as a salient part of the self-concept specifically relates to a desirable behaviour, such as, in this case, healthy eating. A second aim of the study was to test the invariance of the proposed model in two samples of Italian university students (n = 208) and no-student adults (n = 321). At time 1 the questionnaire was made up of measures of TPB constructs, with the addition of past consumption and self-identity as a healthy eater. Both the affective and evaluative components of attitude were assessed. At time 2, only the target behaviour was surveyed. After checking both adequacy of the measurement model and reliability estimates, data were analyzed via structural equation modelling that returned good fit indices. Results showed that intention was positively associated with subjective norm, perceived behavioural control, self-identity and past behaviour. Altogether, they explained 78% of the intention variance in the student group, and 81% in the adult group. After controlling for intention, past behaviour – but not self-identity – was significantly related to the self-reported behaviour, and the model explained 69% and 62% of behaviour variance, respectively. Multi-sample analysis supported model invariance across the two groups. Results and their possible applications are presented and discussed.