An Experimental Test of the Theory of Planned Behavior

The Theory of Planned Behavior (TPB) is one of the leading theories of health behavior, yet supporting evidence is exclusively based on correlational research. This study aims to test the TPB experimentally. N = 579 participants were randomised to receive persuasive messages addressing salient beliefs elicited in a pilot study, following a 2*2*2 factorial design. Participants were randomised to a behavioral-belief-intervention (BBI) or not, a normative-belief-intervention (NBI) or not, and a control-belief-intervention (CBI) or not. The primary outcome was objectively recorded attendance at university sports facilities over 2 months; and the secondary outcomes were post-intervention TPB measures. Main effects of the BBI on attitudes and of the NBI on subjective norm, PBC, attitudes, and intentions were found. The CBI did not alter post-intervention cognitions, but was the only intervention to change behavior not mediated by cognitions. While the findings support the TPB's assumptions on intention formation, behavior change results are not in line with the theory and therefore further question the TPB's leading role in behavioral science.