Augmenting the theory of planned behaviour with the prototype/willingness model: Predictive validity of actor versus abstainer prototypes for adolescents' health-protective and health-risk intentions

Objectives. The present research tested: (a) whether prototype perceptions and descriptive norms from the prototype/willingness model (PWM; Gibbons, Gerrard, Blanton, & Russell, 1998) enhance the prediction of adolescents' intentions to engage in health-protective and health-risk behaviours after variables from the theory of planned behaviour (TPB; Ajzen, 1991) and past behaviour have been taken into account and (b) whether images of the type of person who engages in a health behaviour (actor prototypes) and images of the type of person who does not engage in a health behaviour (abstainer prototypes) have equivalent predictive validity. Design. An experimental design with a single between participants factor (actor versus abstainer prototype) was employed. Method. Participants in this study were 247 school pupils who completed measures of TPB variables, PWM variables and past behaviour in relation to three health-protective and three health-risk behaviours. Results. Findings indicated that PWM variables accounted for a significant proportion of the variance in behavioural intentions after TPB variables and past behaviour had been taken into account (Mean ΔR2 = .05). Perceived similarity to prototypes was the most consistent additional predictor of intention. Actor and abstainer prototypes exhibited equivalent predictive validity. Conclusions. The present research suggests that variables from the PWM, especially prototype similarity, enhance the predictive validity of the TPB. The findings also provide new evidence that acquiring the characteristics of both health and risk images may be goals among adolescents and suggest that both healthy and risky prototypes constitute useful cognitive targets for interventions. © 2006 The British Psychological Society.