What is the Theory of Reasoned Action and how does it explain human behavior?

The Theory of Reasoned Action is a psychological model that aims to explain and predict human behavior. Developed by Martin Fishbein and Icek Ajzen in the late 1960s, this theory suggests that an individual’s behavior is influenced by their attitudes, beliefs, and intentions. It is based on the premise that people are rational decision-makers and their actions are the result of a conscious thought process. In this theory, behavior is seen as a deliberate and rational choice that is influenced by a person’s cognitive processes and social environment. The Theory of Reasoned Action has been widely applied in various fields such as health, marketing, and social psychology, and has provided valuable insights into understanding and modifying human behavior. In this essay, we will explore the key concepts of the Theory of Reasoned Action and how it can be used to explain human behavior.

The theory of reasoned action (TRA), developed by Martin Fishbein and Icek Ajzen (1975, 1980), derived from previous research that started out as the theory of attitude, which led to the study of attitude and behavior. The theory was “born largely out of frustration with traditional attitude-behavior research, much of which found weak correlations between attitude measures and performance of volitional behaviors” (Hale, Householder, & Greene, 2003, p. 259). The key application of the theory of reasoned action is prediction of behavioral intention, spanning predictions of attitude and predictions of behavior. The subsequent separation of behavioral intention from behavior allows for explanation of limiting factors on attitudinal influence (Ajzen, 1980).


Definition and example

Derived from the social psychology setting, the theory of reasoned action (TRA) was proposed by Ajzen and Fishbein (1975 & 1980). The components of TRA are three general constructs: behavioral intention (BI), attitude (A), and subjective norm (SN). TRA suggests that a person’s behavioral intention depends on the person’s attitude about the behavior and subjective norms (BI = A + SN). If a person intends to do a behavior then it is likely that the person will do it.

Behavioral intention measures a person’s relative strength of intention to perform a behavior. Attitude consists of beliefs about the consequences of performing the behavior multiplied by his or her valuation of these consequences. Subjective norm is seen as a combination of perceived expectations from relevant individuals or groups along with intentions to comply with these expectations. In other words, “the person’s perception that most people who are important to him or her think he should or should not perform the behavior in question” (Ajzen and Fishbein, 1975).

To put the definition into simple terms: a person’s volitional (voluntary) behavior is predicted by his/her attitude toward that behavior and how he/she thinks other people would view them if they performed the behavior. A person’s attitude, combined with subjective norms, forms his/her behavioral intention.

Fishbein and Ajzen say, though, that attitudes and norms are not weighted equally in predicting behavior. “Indeed, depending on the individual and the situation, these factors might be very different effects on behavioral intention; thus a weight is associated with each of these factors in the predictive formula of the theory. For example, you might be the kind of person who cares little for what others think. If this is the case, the subjective norms would carry little weight in predicting your behavior” (Miller, 2005, p. 127).

Miller (2005) defines each of the three components of the theory as follows and uses the example of embarking on a new exercise program to illustrate the theory:

Attitudes: the sum of beliefs about a particular behavior weighted by evaluations of these beliefs

You might have the beliefs that exercise is good for your health, that exercise makes you look good, that exercise takes too much time, and that exercise is uncomfortable. Each of these beliefs can be weighted (e.g., health issues might be more important to you than issues of time and comfort).

Subjective norms: looks at the influence of people in one’s social environment on his/her behavioral intentions; the beliefs of people, weighted by the importance one attributes to each of their opinions, will influence one’s behavioral intention

You might have some friends who are avid exercisers and constantly encourage you to join them. However, your spouse might prefer a more sedentary lifestyle and scoff at those who work out. The beliefs of these people, weighted by the importance you attribute to each of their opinions, will influence your behavioral intention to exercise, which will lead to your behavior to exercise or not exercise.

Behavioral intention: a function of both attitudes toward a behavior and subjective norms toward that behavior, which has been found to predict actual behavior.

Your attitudes about exercise combined with the subjective norms about exercise, each with their own weight, will lead you to your intention to exercise (or not), which will then lead to your actual behavior.



The theory of reasoned action has “received considerable and, for the most part, justifiable attention within the field of consumer behavior…not only does the model appear to predict consumer intentions and behavior quite well, it also provides a relatively simple basis for identifying where and how to target consumers’ behavioral change attempts” (Sheppard, Hartwick, & Warshaw, 1988, p. 325).

Hale et al. (2003) say the TRA has been tested in numerous studies across many areas including dieting (Sejwacz, Ajzen, & Fishbein, 1980), using condoms (Greene, Hale, & Rubin, 1997), consuming genetically engineered foods (Sparks, Shepherd, & Frewer, 1995), and limiting sun exposure (Hoffman, 1999).



In its simplest form, the TRA can be expressed as the following equation:

BI = (AB)W1 + (SN)W2


BI = behavioral intention
(AB) = one’s attitude toward performing the behavior
W = empirically derived weights
SN = one’s subjective norm related to performing the behavior

(Source: Hale, 2003)


Limitations and extensions

Sheppard et al. (1988) disagreed with the theory but made certain exceptions for certain situations when they say “a behavioral intention measure will predict the performance of any voluntary act, unless intent changes prior to performance or unless the intention measure does not correspond to the behavioral criterion in terms of action, target, context, time-frame and/or specificity” (p. 325). So, in reference to the above example, if prior to your exercising you learn you have a medical condition, this may affect your behavioral intention.

Sheppard et al. (1988) say there are three limiting conditions on 1) the use of attitudes and subjective norms to predict intentions and 2) the use of intentions to predict the performance of behavior. They are:

  • Goals Versus Behaviors: distinction between a goal intention (an ultimate accomplishment such as losing 10 pounds) and a behavioral intention (taking a diet pill)
  • The Choice Among Alternatives: the presence of choice may dramatically change the nature of the intention formation process and the role of intentions in the performance of behavior
  • Intentions Versus Estimates: there are clearly times when what one intends to do and what one actually expects to do are quite different

Sheppard et al. (1988) suggest “that more than half of the research to date that has utilized the model has investigated activities for which the model was not originally intended” (p. 338). Their expectation was that the model would not fare well in such situations. However, they found the model “performed extremely well in the prediction of goals and in the prediction of activities involving an explicit choice among alternatives.” Thus, Sheppard et al. (1988) concluded that the model “has strong predictive utility, even when utilized to investigate situations and activities that do not fall within the boundary conditions originally specified for the model. That is not to say, however, that further modifications and refinements are unnecessary, especially when the model is extended to goal and choice domains” (p. 338).

Hale et al. (2003) also account for certain exceptions to the theory when they say “The aim of the TRA is to explain volitional behaviors. Its explanatory scope excludes a wide range of behaviors such as those that are spontaneous, impulsive, habitual, the result of cravings, or simply scripted or mindless (Bentler & Speckart, 1979; Langer, 1989). Such behaviors are excluded because their performance might not be voluntary or because engaging in the behaviors might not involve a conscious decision on the part of the actor” (p. 250).


Theory revision

The theory has even been revised and extended by Ajzen himself into the theory of planned behavior. “This extension involves the addition of one major predictor, perceived behavioral control, to the model. This addition was made to account for times when people have the intention of carrying out a behavior, but the actual behavior is thwarted because they lack confidence or control over behavior” (Miller, 2005, p. 127).

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