1. "...there is one primary determinant of behavior, namely the person's intention to perform it. This intention is itself viewed as a function of two determinants

2. This theory provides a framework to study attitudes toward behaviours. According to the theory, the most important determinant of a person's behaviour is behaviour intent. The individual's intention to perform a behaviour is a combination of attitude toward performing the behaviour and subjective norm. The individual's attitude toward the behaviour includes; Behavioural belief, evaluations of behavioural outcome, subjective norm, normative beliefs, and the motivation to comply.

If a person perceives that the outcome from performing a behaviour is positive, she/he will have a positive attitude torward performing that behaviour. The opposite can also be stated if the behaviour is thought to be negative. If relevant others see performing the behaviour as positive and the individual is motivated to meet the exceptions of relevant others, then a positive subjective norm is expected. If relevant others see the behaviour as negative, and the individual wants to meet the expectations of these "others", then the experience is likely to be a negative subjective norm for the individual. Attitudes and subjective norm are measured on scales (as an example the Likert Scale) using phrases or terms such as like/unlike, good/bad, and agree/disagree. The intent to perform a behaviour depends upon the product of the measures of attitude and subjective norm. A positive product indicates behavioural intent.

The Theory of Reasoned Action (TRA) was developed in 1967. During the early 1970s the theory was revised and expanded by Ajzen and Fishbein. By 1980 the theory was used to study human behaviour and develop appropriate interventions.

3. The theory variables and their definitions, as described by Fishbein et al. (1994), are:

Behaviour: A specific behaviour defined by a combination of four components: action, target, context, and time (e.g., implementing a sexual HIV risk reduction strategy (action) by using condoms with commercial sex workers (target) in brothels (context) every time (time).

Intention: The intent to perform a behaviour is the best predictor that a desired behavior will actually occur. In order to measure it accurately and effectively, intent should be defined using the same components used to define behaviour: action, target, context, and time. Both attitude and norms, described below, influence one's intention to perform a behaviour.

Attitude: A person's positive or negative feelings toward performing the defined behaviour.

Norms: A person's perception of other people's opinions regarding the defined behaviour.

Sources:

1. Fishbein summarising Fishbein and Ajzen [1975], Ajzen and Fishbein [1980] Fishbein, Middlestadt and Hitchcock [1991], page 4 in "Developing Effective Behavior Change Interventions", Fishbein M, Univ Of Illinois

2.University of South Florida Community & Family Health site's overview.

3."Behaviour Change - A Summary of Four Major Theories" [PDF]