Aims: An innovation offered by stage models of behaviour change is that of stage-matched interventions. Match-mismatch studies are the primary test of this idea but also the primary test of the validity of stage models. This study aimed at conducting such a test among tobacco smokers using the Social Cognitive Stage Model.
Design: A match-mismatch field-experiment was conducted in which smokers and ex-smokers in different stages were assigned randomly to one of three information conditions.
Participants: Smokers in the pre-contemplation stage, the contemplation stage and the preparation stage, and ex-smokers in the action stage (n = 481), who were recruited through mass media, were assigned randomly to one of three information conditions.
Intervention: In each of the three information conditions, participants received a four- to six-page computer-tailored letter designed to: (1) increase the positive outcome expectations of quitting, (2) decrease the negative outcome expectations of quitting or (3) increase self-efficacy.
Measurements: Forward stage transition was the primary outcome measure, which was assessed 2 months after the participants received the information.
Findings: At the 2-month follow-up, the matched interventions were significantly more effective in stimulating forward stage transition (44.7%) than were mismatched interventions (25.8%; odds ratio = 2.78; confidence interval = 1.85-4.35).
Conclusion: The present study provides experimental support for the benefits of stage-matching and for the validity of the Social Cognitive Stage Model.