This study explored the impact of commitment tactics and individual differences in personality on change-agent participation in a peer-to-peer intervention. The intervention involved approaching bicyclists on campus, discussing the importance of helmet use, and rewarding them with a coupon for a discounted helmet if they signed a promise to wear one.

Change-agent volunteers (n = 82) were trained in one of three commitment conditions to explore their relative impact on approaching a set number of bicyclists. Specifically, change-agents were asked to commit to a personal goal of number of targets they would approach in private, in public to a small group of people, or in public to a large group of people. In addition, change-agents completed measures of the "Big Five" personality traits and susceptibility to social influence tactics to explore their potential influence on intervention performance variables.

No statistically significant differences were found in goal attainment between the commitment conditions. However, 10% more of the change-agents making a public, group commitment met their goal when compared to those who made an individual, private commitment. No significant relation was found between the Big Five personality traits and the number of bicyclist targets approached. However, the Big Five predicted 19% of the variance in the rate of obtaining signed promise cards from bicyclists.

Of the susceptibility to social influence variables, only the Ingratiation score was shown to be useful for predicting change-agent effort, accounting for 18% of the variance in the number of targets approached.

The peer-to-peer intervention was not successful in increasing bicycle helmet use on campus. Limitations of the intervention in comparison to a successful helmet program are discussed.