Chandler wants to give blood at the school blood drive, and he plans to try to do so. But he knows that he will probably be turned away because of a medicine he is on. Chandler has a positive attitude toward blood donation, but what element of the Theory of Planned Behavior inhibits his ability to behave consistently with his attitude?

"Ajzen (1988) introduced the construct ‘perceived behavioral control’ into his theory of planned behavior as a determinant of both behavioral intention and of the behavior itself. On a conceptual basis, perceived behavioral control is similar to self-efficacy—both constructs refer to the person's belief that the behavior in question is under his or her control—but, operationally, perceived behavioral control is often assessed by the ease or difficulty of the behavior (e.g., ‘I find it difficult to exercise three times a week’), while self-efficacy is operationalized by the individual's confidence in being able to carry out the behavior in the face of extenuating circumstances (e.g., ‘I am confident that I can exercise three times a week even when I am away on vacation’)."

Reference: Smelser , Neil, and Paul Baltes. “International Encyclopedia of the Social & Behavioral Sciences.” ScienceDirect, 2001,