Beliefs and Attitudes are a proxy for Behavior
Yes. the above theory of planned behavior is really all about the link between attitudes and behavior. It was proposed as an extension of the (previous) theory of reasoned action, also by Ajzen.
According to the Theory of Reasoned Action, if people evaluate the suggested behavior as positive (Attitude), and if they think their significant others wanted them to perform the behavior (Subjective Norm), this results in a higher intention (motivation) and they are more likely to do so. A high correlation (!) of attitudes and subjective norms to behavioral intention, and subsequently to behavior has been confirmed in many studies.
But a counter argument against the high relationship between behavioral intention and actual behavior was proposed as results of some studies show that behavioral intention not always (!) leads to actual behavior because of circumstantial limitations. Behavioral intention cannot be the exclusive determinant of behavior when an individual’s control over the behavior is incomplete
. For this situation, Ajzen introduced the Theory of Planned Behavior by adding a new component, “Perceived Behavioral Control
”, an individual's perceived ease or difficulty of performing the particular behavior.