The theory of reasoned action (TRA)
(Fishbein & Ajzen, 1975) includes subjective norms and attitude toward the behavior as both influencing behavioral intention, which then directly influences behavior. The theory of planned behavior (TPB) (Ajzen, 1991) adds to these the variable of perceived behavioral control, which, when lacking, can help to explain failure to perform the behavior even when attitude and subjective norms are positive."