Dismantling the theory of planned behavior: evaluating the relative effectiveness of attempts to uniquely change attitudes, norms, and perceived behavioral control

The current study compares the effectiveness of interventions that attempted to uniquely influence hypothesized determinants of behavior in the Theory of Planned Behavior versus some optimal combination of constructs (three constructs vs. four) to increase condom use among intentions and behavior college students. 317 participants (M-age=19.31; SDage=1.31; 53.3% female; 74.1% Caucasian) were randomly assigned to one of seven computer-based interventions. Interventions were designed using the Theory of Planned Behavior as the guiding theoretical framework. 196 (61.8%) completed behavioral follow-up assessments 3-month later. We found that the four construct intervention was marginally better at changing intentions (estimate=-.06, SE=.03, p=.06), but the single construct interventions were more strongly related to risky sexual behavior at follow-up (estimate=.04, SE=.02, p=.05). This study suggests that these constructs may work together synergistically to produce change (ClinicalTrials.gov Number NCT# 02855489).