Why Do Even Strong Intenders Sometimes Fail to Act? Evidence From Protection, Detection, and Risk Health Behaviors

Objective: Behavioral intentions are one of the strongest predictors of health behavior. The current research explored the factors predicting action in those with already strong intentions (i.e., those with the most extreme intention scores). Method: Across four studies on different types of health behavior (physical activity, bowel screening, smoking initiation, COVID-19 protection behaviors), attitudes, norms, perceived behavioral control and past behavior (plus habit in Study 4) were tested as prospective predictors of action in the subsample of participants with extreme (strong) intentions. Results: In Studies 1 (N = 392) and 2 (N = 808) among strong intenders, norms and past behavior were consistent predictors of engaging in objectively assessed physical activity and bowel screening, respectively. In Studies 3 (N = 4,148) and 4 (N = 445) among strong intenders, affective attitudes (only Study 3), descriptive norms, capacity/autonomy, and past behavior were predictors of resisting smoking initiation and engaging in COVID-19 protection behaviors, respectively. Study 4 also showed habit to be a significant predictor of action in strong intenders. Conclusion: This research identifies factors that might be useful targets to promote engagement with health behaviors in those with already strong intentions to act. Future research could usefully test whether targeting these same variables translates into behavior change in those with already strong intentions to act.