Background: The McGuire hierarchy-of-effects (HOE) model, used extensively in mass-media interventions to describe the mechanisms for understanding effects, has not been tested in physical activity campaigns.
Design: Data collected at baseline (2002) and follow-up (2003) surveys in the VERB evaluation were used in structural equation modeling to test pathways and hierarchies of campaign effects.
Setting/participants: Population-based cohort of youth aged 9-13 years (N=2364) for whom complete baseline and follow-up data were available.
Main outcome measures: Awareness of the VERB campaign, understanding of the VERB message, attitude toward being active, outcome expectations, and physical activity participation.
Results: Among youth aged 9-13 years (tweens) in the study cohort, significant paths were identified between awareness and understanding (0.72, p<0.001) and between understanding and being physically active (0.11, p<0.05). At baseline there was a high prevalence of positive attitudes and outcome expectations, and these were not influenced by change in understanding or awareness. Among inactive tweens only, the same paths were identified except that, in this subgroup, attitude was related to physical activity (0.13, p<0.05), and awareness was more strongly related to physical activity than it was for the whole sample (0.14, p<0.01).
Conclusions: These findings provided limited support for the HOE model and suggest that increased awareness and understanding were the key proximal effects that led to behavior change. A distinct sequence of effects, which bypassed attitudes and outcome expectations, was found for these U.S. young people. The findings could inform the design of future campaigns to address youth physical activity.