Control Interactions in the Theory of Planned Behavior: Rethinking the Role of Subjective Norm


  • Francesco La Barbera
  • Icek Ajzen


Research with the theory of planned behavior (TPB) has typically treated attitude (ATT), subjective norm (SN), and perceived behavioral control (PBC) as independent predictors of intention (INT). However, theoretically, PBC moderates the effects of ATT and SN on intention. In three studies dealing with different behaviors (voting, reducing household waste, and energy consumption) we show that greater PBC tends to strengthen the relative importance of ATT in the prediction of intention, whereas it tends to weaken the relative importance of SN. The latter pattern was observed in relation to injunctive as well as descriptive subjective norms, and it may help explain the relatively weak relation between SN and INT frequently observed in TPB studies.