Combining Self-Affirmation and Implementation Intentions: Evidence of Detrimental Effects on Behavioral Outcomes

Background There is limited evidence that self-affirmation manipulations can promote health behavior change. Purpose The purpose of this study was to explore whether the efficacy of a self-affirmation manipulation at promoting exercise could be enhanced by an implementation intention intervention. Methods Participants (Study 1N =120, Study 2N =116) were allocated to one of four conditions resulting from the two (self-affirmation manipulation: no affirmation, affirmation) by two (implementation intention manipulation: no implementation intention, implementation intention) experimental design. Exercise behavior was assessed 1 week post intervention. Results Contrary to prediction, those participants receiving both manipulations were significantly less likely to increase the amount they exercised compared to those receiving only the self-affirmation manipulation. Conclusion Incorporating an implementation intention manipulation alongside a self-affirmation manipulation had a detrimental effect on exercise behavior; participants receiving both manipulations exercised significantly less in the week following the intervention