The Best Laid Plans: Planning Skill Determines the Effectiveness of Action Plans and Implementation Intentions

Theories of action control emphasise the importance of planning, but plans are not universally beneficial. The present study investigates whether the effectiveness of plans depends upon the skill of the planner. Study 1 prospectively predicted changes in unhealthy snacking behaviour over 1 week from intentions, action planning and performance on a standardised cognitive test of planning skill (n = 72). Study 2 experimentally randomised skilled and poor planners to receive (or not) a planning intervention before completing an online food diary (n = 144) Spontaneously generated action plans about snacking explained significantly more variance in subsequent snacking if produced by a skilled rather than a poor planner. The planning intervention (implementation intention) significantly improved goal attainment but only in poor planners. Plans are only as good as the people who make them. Poor planners' plans do not help achieve goals. Planning interventions can compensate for a lack of planning skill.