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Theory of Planned Behavior

The Theory of Planned Behavior is a theory used to understand and predict behaviors, which posits that behaviors are immediately determined by behavioral intentions and under certain circumstances, perceived behavioral control. Behavioral intentions are determined by a combination of three factors: attitudes toward the behavior, subjective norms, and perceived behavioral control.[1]

The theory of planned behavior (TPB) has been used successfully to explain and predict behavior in a multitude of behavioral domains, from physical activity to drug use, from recycling to choice of travel mode, from safer sex to consumer behavior, and from technology adoption to protection of privacy, to name but a few (for meta‐analytic syntheses of some of this research, see e.g., Albarracin, Fishbein, & Goldestein de Muchinik, 1997; Armitage & Conner, 1999; Hagger, Chatzisarantis, & Biddle, 2002; Hirschey et al., 2020; McDermott et al., 2015; Riebl et al., 2015; Winkelnkemper, Ajzen, & Schmidt, 1919). The following description of the TPB is adapted from Ajzen and Kruglanski (2019).


Theory of Planned Behavior - Historical Background[2]

Extension from the theory of reasoned action
Icek Ajzen (1985) proposed TPB in his chapter "From intentions to actions: A theory of planned behavior." TPB developed out of Theory of Reasoned Action, a theory first proposed in 1980 by Martin Fishbein and Ajzen. TRA was in turn grounded in various theories bearing on attitude and attitude change, including learning theories, expectancy-value theories, attribution theory, and consistency theories (e.g., Heider's balance theory, Osgood and Tannenbaum's congruity theory, and Festinger's dissonance theory). According TRA, if an individual evaluates a suggested behavior as positive (attitude), and if he or she believes significant others want the person to perform the behavior (subjective norm), the intention (motivation) to perform the behavior will be greater and the individual will be more likely to perform the behavior. Attitudes and subjective norms are highly correlated with behavioral intention; behavioral intention is correlated with actual behavior.

Research, however, shows that behavioral intention does not always lead to actual behavior. Because behavioral intention cannot be the exclusive determinant of behavior where an individual's control over the behavior is incomplete, Ajzen introduced TPB by adding to TRA the component "perceived behavioral control." In this way he extended TRA to better predict actual behavior.

Perceived behavioral control refers to the degree to which a person believes that he or she can perform a given behavior. Perceived behavioral control involves the perception of the individual's own ability to perform the behavior. In other words, perceived behavioral control is behavior- or goal-specific. That perception varies by environmental circumstances and the behavior involved. The theory of planned behavior suggests that people are much more likely to intend to enact certain behaviors when they feel that they can enact them successfully. The theory has thus improved upon TRA.

Extension of self-efficacy
Along with attitudes and subjective norms (which make up TRA), TPB adds the concept of perceived behavioral control, which grew out of self-efficacy theory (SET). The construct of self-efficacy was proposed by Bandura in 1977, in connection to social cognitive theory. Self-efficacy refers to a person's expectation or confidence that he or she can master a behavior or accomplish a goal; an individual has different levels of self-efficacy depending upon the behavior or goal in question. Bandura distinguished two distinct types of goal-related expectations: self-efficacy and outcome expectancy. He defined self-efficacy as the conviction that one can successfully execute the behavior required to produce the outcome in question. Outcome expectancy refers to a person's estimation that a given behavior will lead to certain outcomes. Bandura advanced the view that self-efficacy is the most important precondition for behavioral change, since it is key to the initiation of coping behavior.

Previous investigations have shown that a person's behavior is strongly influenced by the individual's confidence in his or her ability to perform that behavior. As self-efficacy contributes to explanations of various relationships among beliefs, attitudes, intentions, and behavior, TPB has been widely applied in health-related fields such as helping preadolescents to engage in more physical activity, thereby improving their mental health, and getting adults to exercise more.


Constructs of the Theory of Planned Behavior[3]

The theory of planned behavior (TPB) has been used successfully to explain and predict behavior in a multitude of behavioral domains, from physical activity to drug use, from recycling to choice of travel mode, from safer sex to consumer behavior, and from technology adoption to protection of privacy, to name but a few (for meta‐analytic syntheses of some of this research, see e.g., Albarracin, Fishbein, & Goldestein de Muchinik, 1997; Armitage & Conner, 1999; Hagger, Chatzisarantis, & Biddle, 2002; Hirschey et al., 2020; McDermott et al., 2015; Riebl et al., 2015; Winkelnkemper, Ajzen, & Schmidt, 1919). The TPB states that behavioral achievement depends on both motivation (intention) and ability (behavioral control). It distinguishes between three types of beliefs - behavioral, normative, and control. The TPB is comprised of six constructs that collectively represent a person's actual control over the behavior.

  • Attitudes - This refers to the degree to which a person has a favorable or unfavorable evaluation of the behavior of interest. It entails a consideration of the outcomes of performing the behavior.
  • Behavioral intention - This refers to the motivational factors that influence a given behavior where the stronger the intention to perform the behavior, the more likely the behavior will be performed.
  • Subjective norms - This refers to the belief about whether most people approve or disapprove of the behavior. It relates to a person's beliefs about whether peers and people of importance to the person think he or she should engage in the behavior.
  • Social norms - This refers to the customary codes of behavior in a group or people or larger cultural context. Social norms are considered normative, or standard, in a group of people.
  • Perceived power - This refers to the perceived presence of factors that may facilitate or impede performance of a behavior. Perceived power contributes to a person's perceived behavioral control over each of those factors.
  • Perceived behavioral control - This refers to a person's perception of the ease or difficulty of performing the behavior of interest. Perceived behavioral control varies across situations and actions, which results in a person having varying perceptions of behavioral control depending on the situation. This construct of the theory was added later, and created the shift from the Theory of Reasoned Action to the Theory of Planned Behavior.


Theory of Planned Behavior
source: Boston University


Understanding the Theory of Planned Behavior[4]

The following description of the TPB is adapted from Ajzen and Kruglanski (2019).

  • The principle of compatibility: The TPB starts with an explicit definition of the behavior of interest in terms of its target, the action involved, the context in which it occurs, and the time frame. Each of these elements can be defined at varying levels of specificity or generality. However, once the behavior has been defined, all other constructs in the theory must correspond to the behavior in all four elements. This is known as the principle of compatibility (Ajzen, 1988). For example, to study technology acceptance, an investigator may define the behavior of interest at a low level of generality, such as “installing (action) a webcam monitor (target) at home (context) in the next three months (time frame).” Alternatively, the investigator may be interested in technology acceptance at a more general level and define the behavior as “buying (action) an internet‐connected device (target) in the next three months (time).” Note that the target has been expanded to include a broad range of devices, not just a webcam, and that the context is left unspecified. The particular behavioral definition adopted determines how all constructs in the TPB are to be formulated and measured.
  • Proximal determinants of behavior: The immediate antecedent of behavior in the TPB is the intention to perform the behavior in question; the stronger the intention, the more likely it is that the behavior will follow. To return to the above example, we could assess the intention to buy an internet‐connected device in the next 3 months and determine whether participants did or did not implement their intentions. However, unanticipated events; insufficient time, money, or resources; lack of requisite skills; and a multitude of other factors may prevent people from acting on their intentions. The degree to which people have actual control over the behavior depends on their ability to overcome barriers of this kind and on the presence of such facilitating factors as past experience and assistance provided by others. In light of these considerations, the TPB postulates that degree of behavioral control moderates the effect of intention on behavior: The greater the actor's control over the behavior, the more likely it is that the intention will be carried out (for a discussion of the intention x control interaction, see Fishbein & Ajzen, 2010, pp. 65–66).
  • Determinants of intentions: According to the TPB, behavioral intentions are determined by three factors: attitude toward the behavior, subjective norm concerning the behavior, and perceived behavioral control. In the current formulation of the theory, a favorable attitude and a supportive subjective norm provide the motivation to engage in the behavior but a concrete intention to do so is formed only when perceived control over the behavior is sufficiently strong. These notions are described in greater detail below.
    • Attitude toward the behavior: The TPB relies on an expectancy‐value formulation to describe the formation of attitude toward a behavior. Specifically, attitude toward the behavior is assumed to be a function of readily accessible beliefs regarding the behavior's likely consequences, termed behavioral beliefs. A behavioral belief is the person's subjective probability that performing a behavior of interest will lead to a certain outcome or provide a certain experience, for example, the belief that wearing a heart monitor (the behavior) can detect heart arrhythmia (the outcome) or is inconvenient (the experience). In their aggregate, behavioral beliefs are theorized to produce a positive or negative attitude toward the behavior. Specifically, the positive or negative valence of each anticipated outcome or experience contributes to the overall attitude in direct proportion to the subjective probability that the behavior will produce the outcome or experience in question. This expectancy‐value model is represented in Equation (1). As can be seen, the strength of each accessible belief (b) is multiplied by the subjective evaluation (e) of the outcome or experience and the resulting products are summed. A person's attitude (ATT) is expected to be directly proportional (∝) to this composite belief index.
      ATT∝∑b_ie_i

    • Subjective norm: We can distinguish between two types of normative belief: injunctive and descriptive (see Fishbein & Ajzen, 2010). An injunctive normative belief is the expectation or subjective probability that a given referent individual or group (e.g., friends, family, spouse, coworkers, one's physician or supervisor) approves or disapproves of performing the behavior under consideration. Descriptive normative beliefs, on the other hand, are beliefs as to whether important others themselves perform the behavior. Both types of beliefs contribute to the overall perceived social pressure to engage in the behavior or subjective norm. As shown in Equation (2), each accessible normative belief (n) with respect to a given social referent, whether injunctive or descriptive, contributes to subjective norm (SN) in interaction with the referent's importance or significance (s) to the individual, and the subjective norm is directly proportionate to the sum of the n × s products.
      SN∝∑n_is_i

    • Perceived behavioral control: Just as attitudes are assumed to be based on accessible behavioral beliefs and subjective norms on accessible normative beliefs, perceived behavioral control is assumed to be based on accessible control beliefs. These beliefs are concerned with the presence of factors that can facilitate or impede performance of the behavior. Control factors include required skills and abilities; availability or lack of time, money, and other resources; cooperation by other people; and so forth. A control belief is defined as a person's subjective probability that a given facilitating or inhibiting factor will be present in the situation of interest. Each control belief contributes to perceived behavioral control in interaction with the factor's perceived power to facilitate or impede performance of the behavior. Perceived behavioral control (PBC) is directly proportional to the composite score derived by summing the products of control belief strength (c) times perceived power (p) over all accessible control factors. In the TPB, perceived behavioral control is assumed to moderate the influence of attitude and subjective norm on intention, and actual behavioral control is assumed to moderate the effect of intention on behavior. That is, a favorable attitude and a supportive subjective norm are said to lead to the formation of a favorable behavioral intentions to the extent that people believe that they are capable of performing the behavior in question. Similarly, as noted earlier, people are expected to be able to act on their intentions to the extent that they have control over performance of the behavior. When knowledge about actual behavioral control is limited, perceived behavioral control can be used as a proxy to aid in the prediction of behavior under the assumption that perceived control reflects actual control reasonably well.
      PBC∝∑c_ip_i

  • Feedback effects: Performance of a behavior results in information about the actual (as opposed to anticipated) outcomes, experiences, reactions by significant others, as well as about facilitating or impeding factors encountered by the actor. This feedback is likely to change some of the behavioral, normative, and control beliefs and thus influence future intentions regarding the behavior in question. For example, a woman may initially believe that working out before work will be invigorating, that it will be applauded by her boss and coworkers, and that she can get to the gym early enough to be at work on time. Yet on her initial attempts she discovers that it takes her much longer to get to the gym than anticipated due to heavy rush hour traffic, that working out at the gym leaves her tired and dispirited rather than invigorated, and that neither her coworkers nor her supervisor express support for this behavior. These changes in behavioral, normative, and control beliefs may result in less favorable attitudes and subjective norms as well as in a lower sense of behavioral control, all of which may lead her to abandon her intention to work out at the gym prior to going to work.


Theory of Planned Behavior Example[5]

A retail store has just launched its online store. While the intention is that people move from buying in-store to online, nobody is behaving this way. Let’s find out why.

A survey of existing customers, shaped by the Theory of Planned Behavior, is used to understand customer beliefs about online shopping. By asking a set of open-ended questions, the relevant barriers and attitudes become clear.

  • Attitudes: In the survey, people share their attitudes towards online shopping. Some customers understand the convenience of shopping online, while others want to buy in-store rather than wait for delivery. Many of the store’s customers are older and believe it is not safe to use a credit card online.
  • Subjective Norms: Respondents say that their friends and family who have tried shopping online, have not had problems with making a purchase. Respondents noted that their younger friends actually prefer to buy online.
  • Perceived Behavioral Control: When asked about barriers to shopping online, many older customers shared that they find technology confusing, and this is preventing them from making a purchase. The survey also threw up some other issues:
    • Some people like to touch and inspect products before they buy them.
    • Most people were not aware that it was possible to buy the store’s products online.
  • Intention: In the survey, many customers highlighted that the would like to use the online store but hadn’t done so yet simply because they found it all a little overwhelming and daunting.

Example Conclusions
Now the factors that influence customers shopping online are understood, what can be done about it?

To address the issues raise the store could:

  • Customers who create an instore account are able to register their credit card details. When making online orders, they no longer have to enter credit card details.
  • To help build awareness of the online store, in-store checkout clerks remind customers they can buy products online.
  • To bridge the intention gap where customers want to use the online store but find it overwhelming, the store offers people to have someone in-store walk them through the whole online process for their first online purchase.

By implementing actions to address all of the factors that influence behavior according to the Theory of Planned Behavior, the store should begin to see a noticeable uptake in people using its online store.

Although this example examines the theory from a business perspective, the model is commonly used in public health planning, for example, such as where you are endeavoring to encourage the population to eat a healthier diet.


Evaluation of the Theory[6]

Internal Consistency, Theory, Utility
The basic Theory of Planned Behavior has a strong level of internal consistency, however, when extrapolated to larger fields or more specific applications the consistency becomes more challenging. The relationships between variables can be difficult to measure and the causation may be difficult to determine. The analytical and regressive nature of the data analysis does lead to relatively consistent results over time. While the theory does make some postulations about non-planned behavior, it may be difficult to conclude that most planned behavior is based on intention.

The theory’s primary utilities lie in predicting behavior. By collecting or modeling data, researchers can utilize any information they have to predict how an individual or group will behave.

Applications<
Understanding how people actually behave is an integral aspect of Consumer Economics. Truthfully, every aspect of economics would benefit from looking at how individuals and groups actually behave instead of simply assuming rationality. The primary utility in consumer economics is simply being able to understand and determine which variables are most important in understanding consumer intention that is followed by action.

Evaluating how consumers react to marketing is a major implication of planned behavior. The decision making process is complicated in any scenario, but, by observing the influential variables, researchers can decipher what is truly most important in the consumer decision making process. The final outcomes can be used to study anything from why people smoke cigarettes to why they stay married or even why they continue to make poor financial choices on a consistent basis.


Limitations of the Theory of Planned Behavior[7]

There are several limitations of the TPB, which include the following:

  • It assumes the person has acquired the opportunities and resources to be successful in performing the desired behavior, regardless of the intention.
  • It does not account for other variables that factor into behavioral intention and motivation, such as fear, threat, mood, or past experience.
  • While it does consider normative influences, it still does not take into account environmental or economic factors that may influence a person's intention to perform a behavior.
  • It assumes that behavior is the result of a linear decision-making process, and does not consider that it can change over time.
  • While the added construct of perceived behavioral control was an important addition to the theory, it doesn't say anything about actual control over behavior.
  • The time frame between "intent" and "behavioral action" is not addressed by the theory.

The TPB has shown more utility in public health than the Health Belief Model, but it is still limiting in its inability to consider environmental and economic influences. Over the past several years, researchers have used some constructs of the TPB and added other components from behavioral theory to make it a more integrated model. This has been in response to some of the limitations of the TPB in addressing public health problems.


See Also

Technology Acceptance Model (TAM)
Integrated Behavioral Model
Self-Efficacy Theory
Theory E and Theory O
Theory X Theory Y
Theory Z
Theory of Bisociation
Theory of Constraints
Theory of Inventive Problem Solving
Theory of Mechanistic and Organic Systems
Theory of Needs
Theory of Reasoned Action
Complexity Theory
Balance Theory
Expectancy Theory
Congruity Theory
Game Theory
Organizational Theory
Bureaucratic Theory
Gestalt theory
Graves Value Theory
Microeconomic Theory
Systems Theory
Stakeholder Theory
Stewardship Theory
Contingency Theory
Shareholder Theory
Agency Theory
Information Theory
Dempster Shafer (D-S) Theory
Resource Scarcity Theory
General Systems Theory (GST)
Goal Setting Theory
Upper Echelons Theory
Probability Theory
Modern Portfolio Theory (MPT)
Lewin/Schein's Change Theory
Diffusion of Innovation Theory
Decision Theory
Cultivation Theory
Persuasion Theory
Trickle-Down Theory
Catastrophe Theory
Plausibility Theory
Chaos Theory
Attribution Theory
ERG Theory
Limited Effects Theory
Scientific Management Theory
Social Judgment Theory
Black Swan Theory
Resource Dependence Theory
Dynamical Systems Theory


References

  1. Definition - What Does the Theory of Planned Behavior Mean? Matthew P. H. Kan, Leandre R. Fabrigar
  2. History of the Theory of Planned Behavior Wikipedia
  3. The Six Constructs of the Theory of Planned Behavior Boston University
  4. Understanding the Theory of Planned Behavior Icek Ajzen
  5. Theory of Planned Behavior Example EPM
  6. Evaluation of the Theory Simple Economist
  7. Limitations of the Theory of Planned Behavior bu.edu