Tell Me a Story About Healthy Snacking and I Will Follow: Comparing the Effectiveness of Self-Generated Versus Message-Aided Implementation Intentions on Promoting Healthy Snacking Habits Among College Students.

In the context of healthy snacking, this study examines whether the quality of mental imagery determines the effectiveness of combining the implementation intention (II) intervention with mental imagery. This study further explores whether providing narrative healthy snacking scenarios prior to forming an II enhances people's mental imagery experience when they are not motivated to snack healthfully. A 2 × 2 factorial design was employed to test the main effect of providing healthy snacking scenarios prior to II formation, and whether such effect depends on people's motivation level. The results from the experiment (N =148) showed significant main as well as interaction effects of the manipulation (with vs. without reading healthy snacking scenarios prior to II formation) and motivation level on ease and vividness of mental imagery. The regression model with the experiment and follow-up survey data (n = 128) showed a significant relationship between ease of mental imagery and actual snacking behavior after controlling for habit strength. The findings suggest that adding a narrative message to the II intervention can be useful, especially when the intervention involves mental imagery and invites less motivated people.