An extended version of the theory of reasoned action, incorporating a construct of perceived behavioural control and thus enabling predictions to be made of actions that are under incomplete volitional control. In the theory, perceived behavioural control is a function of one's beliefs about how likely it is that one has the resources and opportunities required to perform the behaviour. The theory was formulated by the Polish-born US psychologist Icek Ajzen (born 1942) and expounded in his book Attitudes, Personality, and Behavior (1988) and in an article in the journal Organizational Behavior and Human Decision Processes (1991). US theory of planned behavior. TPB abbrev.