Theory of Planned Behavior

Based on the theory of reasoned action, the theory of planned behavior (TPB) was first described by social psychologist Icek Ajzen in 1985. The theory posits that someone’s behavior is determined by their intention to perform that behavior and in some cases, their perceived level of behavioral control.

Aspect	Explanation
Concept Overview	– The Theory of Planned Behavior (TPB) is a well-established social psychology theory developed by psychologist Icek Ajzen. It aims to explain and predict human behavior by considering the influence of attitudes, subjective norms, and perceived behavioral control. According to TPB, these factors collectively shape an individual’s intention to engage in a specific behavior, which, in turn, leads to the actual behavior. TPB is widely applied in various fields, including psychology, health promotion, marketing, and social sciences, to understand and modify human behavior.
Key Components	– TPB consists of three core components: 1. Attitudes (A): Refers to an individual’s favorable or unfavorable evaluation of the behavior in question. Positive attitudes increase the likelihood of performing the behavior, while negative attitudes decrease it. 2. Subjective Norms (SN): Represent the perceived social pressure or approval related to the behavior. The influence of significant others, such as family, friends, or colleagues, is considered. 3. Perceived Behavioral Control (PBC): Reflects the perceived ease or difficulty of performing the behavior. It considers internal and external factors that may hinder or facilitate the behavior.
Behavioral Intention	– The central concept in TPB is behavioral intention, which is the individual’s willingness and readiness to perform a specific behavior. Behavioral intention serves as a strong predictor of whether the behavior will actually be carried out. The strength of intention is influenced by attitudes, subjective norms, and perceived behavioral control. Strong intentions are more likely to result in the desired behavior.
Calculating Intention	– TPB posits that behavioral intention is calculated as follows: Intention (I) = Attitudes (A) x Subjective Norms (SN) x Perceived Behavioral Control (PBC). In this formula, each component has a specific weight or influence on intention, and their interplay determines the strength of intention. Positive attitudes, subjective norms, and perceived behavioral control contribute to higher intention, while negative factors reduce it.
Influence on Behavior	– According to TPB, intention is a direct precursor to behavior. However, it also recognizes that external factors, such as resource constraints or unexpected events, can influence the translation of intention into action. While strong intention increases the likelihood of behavior, it does not guarantee it. External factors and constraints may either facilitate or hinder the actual performance of the behavior. Thus, TPB offers insights into the factors that mediate between intention and behavior.
Applications	– TPB has broad applications in various fields: 1. Health Promotion: Understanding factors influencing health-related behaviors like smoking cessation or exercise. 2. Marketing: Shaping consumer behavior and product adoption. 3. Environmental Conservation: Encouraging eco-friendly actions. 4. Social Policy: Influencing policy compliance and civic engagement. 5. Organizational Behavior: Explaining employee behavior and decision-making. TPB guides interventions and strategies to change behavior effectively.
Limitations	– TPB has some limitations: 1. Lack of Specificity: It may not provide detailed insights into the specific reasons behind attitudes, subjective norms, or control factors. 2. Volitional Behavior: It is better suited for behaviors that are under conscious control rather than automatic or impulsive actions. 3. Cultural Variations: Cultural factors can influence the applicability of TPB across diverse populations. 4. Temporal Factors: TPB does not account for changes in intention over time. It assumes stable intention and behavior relationships.
Modification of Behavior	– To modify behavior using TPB, interventions can focus on changing attitudes, subjective norms, or perceived behavioral control: 1. Attitude Change: Providing information to create more positive attitudes toward the behavior. 2. Normative Influence: Shaping subjective norms by highlighting the approval of significant others. 3. Empowerment: Enhancing perceived behavioral control through skill-building or resource provision. Effective interventions consider the specific determinants of the target behavior.
Collecting Data	– Data collection for TPB involves surveys or interviews to assess individuals’ attitudes, subjective norms, perceived behavioral control, and behavioral intentions regarding a specific behavior. The data are then analyzed to understand the relationships among these components and predict behavior. Various scales and questionnaires are available for measuring TPB constructs. Researchers use these tools to gather insights and develop tailored interventions.
Criticisms and Updates	– TPB has evolved over time, with criticisms leading to refinements. Some criticisms include the need for more precise measurement of its components and the recognition that other factors, such as emotions or habit, can influence behavior. Researchers have developed extensions and variations of TPB to address these limitations, making it a flexible and adaptable theory for understanding and modifying human behavior in various contexts.

Table of Contents

Understanding the theory of planned behavior

The theory of planned behavior posits that all behaviors are conscious, planned, and reasoned. In other words, it assumes that the individual has deliberate control over their actions.

Someone’s intention to perform a specific behavior is fundamental to the theory of planned behavior. In a subsequent 1991 article in the journal Organizational Behavior and Human Decision Processes, Ajzen described intention as the “motivational factors that influence a behavior; they are indications of how hard people are willing to try, of how much an effort they are planning to exert, in order to perform the behavior.”

Since the theory helps practitioners understand and predict human behavior, its applications are almost unlimited.

Nevertheless, it is particularly popular in healthcare contexts such as family planning, addiction, birth control, and disease prevention.

TPB has also been applied to entrepreneurial intention (EI). In a study of 528 business administration undergraduates in Turkey, researchers found that students with prior start-up experience were more likely to engage in entrepreneurial behavior because of increased levels of self-efficacy and personal attitude toward entrepreneurship itself.

From the results, the researchers noted that this behavioral predictor could be harnessed by policy-makers as a way to drive innovation and innovative thinking within their respective economies.

What influences behavioral intention in the TPB?

Behavioral intention is influenced by three factors.

1 – Personal attitudes

The sum of an individual’s attitudes, knowledge, and prejudices toward a specific behavior (both positive and negative).

Someone’s attitude toward smoking, for example, may include that tobacco is a relaxing pastime that also makes them smell and wake up with a hacking cough in the morning.

2 – Subjective norms

The perception of the attitudes of other people toward the behavior. The smoker may perceive that their friends and family think their habit is addictive and harmful to their health.

3 – Perceived behavioral control

The extent to which the individual believes they can control their behavior. This may be influenced by factors such as their perceived level of ability and determination or the number of support services available to them.

Importantly, TPB believes this perception affects:

The individual’s intention to behave a certain way. That is, the more control one believes they have over their behavior, the stronger the intention to perform that behavior.
The behavior directly. When an individual perceives that there is more control, they tend to exert effort for longer to succeed.

How can the theory of planned behavior be used?

The theory of planned behavior is the most used model in healthcare psychology and intervention campaigns.

If we return to the previous example of the smoker, let’s imagine that the individual is 18 years old and part of a friend group where most others also smoke. Based on this, the teenager may come to the mistaken conclusion that smoking is the norm.

Using TPB, the government could develop an anti-smoking campaign where the true percentage of teenage smokers was clarified.

In America, for example, a 2021 CDC study found that just 1.9% of high school students had smoked cigarettes in the previous 30 days.

When the teenage smoker is exposed to the true extent of smoking among those in their age group, their subjective norm will likely change. In other words, they will perceive that the vast majority of people don’t smoke and potentially see their behavior as undesirable.

Key takeaways:

The theory of planned behavior posits that all behaviors are conscious, planned, and reasoned. The theory posits that someone’s behavior is determined by their intention to perform that behavior and in some cases, their perceived level of behavioral control.
The theory of planned behavior helps practitioners understand and predict human behavior, so its applications are almost unlimited. It is mostly used in healthcare contexts but is also seen in entrepreneurship, innovation, and economic development.
Behavioral intention in the theory of planned behavior is determined by three variables: personal attitudes, subjective norms, and perceived behavioral control. By understanding these variables, organizations and governments can predict behavior and create interventions that nudge individuals toward more beneficial behaviors.

Key Highlights

Origin and Definition: The Theory of Planned Behavior (TPB) was introduced by social psychologist Icek Ajzen in 1985 as an extension of the Theory of Reasoned Action. It suggests that behaviors are driven by an individual’s intention to perform that behavior and their perceived level of control over it.
Conscious and Reasoned Behavior: TPB posits that all behaviors are conscious, planned, and reasoned. It assumes that individuals have deliberate control over their actions.
Behavioral Intention: Intention to perform a specific behavior is a central concept in TPB. It reflects the motivational factors that influence how hard an individual is willing to try and how much effort they plan to exert to perform a behavior.
Applications: TPB has versatile applications in understanding and predicting human behavior. It is widely used in healthcare contexts such as family planning, addiction, birth control, and disease prevention. It’s also applied to areas like entrepreneurship, innovation, and economic development.
Healthcare Psychology and Interventions: TPB is commonly employed in healthcare psychology and intervention campaigns. It helps design interventions that guide individuals toward beneficial behaviors.
Influential Factors in Behavioral Intention:
- Personal Attitudes: The individual’s positive and negative attitudes, knowledge, and prejudices toward a specific behavior.
- Subjective Norms: The perception of how others view the behavior, including friends, family, and societal norms.
- Perceived Behavioral Control: The individual’s belief in their ability to control their behavior, influenced by factors like ability, determination, and available support services.
Effect on Intention and Behavior:
- High perceived behavioral control strengthens an individual’s intention to perform a behavior.
- Strong intention leads to more effort exerted in performing the behavior.
Practical Example: Suppose a teenager smokes because they perceive smoking as the norm among their friends. By correcting this perception and showing the actual prevalence of smoking, their subjective norm may change, making the behavior less desirable.

Related Framework	Description	When to Apply
Health Belief Model	The Health Belief Model (HBM) is a psychological framework that explores individuals’ beliefs and perceptions about health-related behaviors. Similar to the Theory of Planned Behavior (TPB), the HBM examines the factors influencing individuals’ decision-making and behavior change. The HBM emphasizes perceived susceptibility, severity, benefits, barriers, and cues to action as determinants of health-related behaviors. By understanding individuals’ perceptions and beliefs about health risks and benefits, the HBM provides insights into designing interventions to promote health behavior change.	When developing health promotion campaigns, interventions, or public health initiatives, applying the Health Belief Model to understand individuals’ beliefs, perceptions, and motivations related to health behaviors, thus informing the design of effective strategies to promote behavior change and improve health outcomes.
Transtheoretical Model	The Transtheoretical Model (TTM) of behavior change explores the stages individuals go through when adopting new behaviors. Similar to the Theory of Planned Behavior (TPB), the TTM examines factors influencing behavior change, including attitudes, intentions, and environmental factors. The TTM identifies stages of change, processes of change, self-efficacy, and decisional balance as key constructs that influence behavior change. By understanding individuals’ readiness to change and addressing barriers at different stages, the TTM provides a framework for designing tailored interventions to support behavior change across various domains.	When designing behavior change interventions or programs, applying the Transtheoretical Model to assess individuals’ readiness to change, identify barriers and facilitators at different stages of change, and tailor interventions to address their specific needs and motivations, thus enhancing the effectiveness of behavior change efforts in promoting healthy behaviors and lifestyle changes.
Social Cognitive Theory	Social Cognitive Theory (SCT) explores the role of social learning, cognitive processes, and environmental influences in shaping behavior. Similar to the Theory of Planned Behavior (TPB), SCT examines how individuals’ beliefs, attitudes, and self-efficacy influence behavior. SCT emphasizes observational learning, self-regulation, and reciprocal determinism as key factors in behavior change. By understanding the interactions between individual, environmental, and behavioral factors, SCT provides insights into designing interventions that promote behavior change and skill development across diverse contexts.	When designing interventions or programs to promote behavior change, applying Social Cognitive Theory to examine the role of observational learning, self-efficacy, and environmental influences in shaping behavior, thus informing the design of effective strategies to enhance individuals’ skills, self-regulation, and motivation for behavior change in various settings and contexts.
Social Ecological Model	The Social Ecological Model (SEM) examines how individual behavior is influenced by multiple levels of social and environmental factors. Similar to the Theory of Planned Behavior (TPB), the SEM acknowledges the importance of individual attitudes and intentions in shaping behavior. However, the SEM expands the focus to include interpersonal, organizational, community, and policy-level factors that influence behavior change. By recognizing the interconnectedness of factors across different levels of the social ecology, the SEM provides a comprehensive framework for designing multilevel interventions to promote behavior change and address public health issues.	When developing public health interventions, policy initiatives, or community programs, applying the Social Ecological Model to consider the influence of individual, interpersonal, organizational, community, and policy-level factors on behavior change, thus informing the design of comprehensive, multilevel interventions that address multiple determinants of health behavior and promote positive changes at the individual and population levels.
Self-Determination Theory	Self-Determination Theory (SDT) examines the role of intrinsic motivation, autonomy, and psychological needs in driving behavior. Similar to the Theory of Planned Behavior (TPB), SDT explores individuals’ attitudes, intentions, and motivation to engage in behavior. SDT emphasizes the importance of satisfying basic psychological needs for autonomy, competence, and relatedness in promoting behavior change and well-being. By understanding individuals’ intrinsic motivations and psychological needs, SDT provides insights into fostering autonomous motivation and supporting behavior change in various domains.	When designing interventions or programs aimed at promoting behavior change or enhancing motivation, applying Self-Determination Theory to assess individuals’ intrinsic motivations, autonomy, and psychological needs, thus informing the design of strategies that support autonomy, competence, and relatedness to foster intrinsic motivation and promote sustainable behavior change across different contexts and populations.
Goal Setting Theory	Goal Setting Theory explores the cognitive processes involved in setting and pursuing goals, as well as the factors influencing goal attainment. Similar to the Theory of Planned Behavior (TPB), Goal Setting Theory examines individuals’ intentions and motivations to achieve specific outcomes. Goal Setting Theory emphasizes the importance of setting clear, challenging, and achievable goals in motivating behavior change and performance improvement. By understanding the mechanisms underlying goal setting and goal striving, Goal Setting Theory provides insights into designing effective goal-setting interventions to facilitate behavior change and goal achievement.	When designing behavior change interventions, performance improvement programs, or personal development initiatives, applying Goal Setting Theory to set clear, challenging goals and provide feedback and support to individuals in pursuing their goals, thus enhancing motivation, focus, and commitment to behavior change and goal attainment across various domains and settings.
Theory of Reasoned Action	The Theory of Reasoned Action (TRA) explores the influence of attitudes and subjective norms on individuals’ behavioral intentions and decisions. Similar to the Theory of Planned Behavior (TPB), TRA examines the determinants of behavior, including attitudes, subjective norms, and perceived behavioral control. TRA posits that individuals’ intentions to engage in behavior are influenced by their beliefs about the behavior and the perceived expectations of significant others. By understanding the factors shaping individuals’ behavioral intentions, TRA provides insights into predicting and influencing behavior change across different domains.	When studying individuals’ behavioral intentions, attitudes, and subjective norms, applying the Theory of Reasoned Action to examine the influence of beliefs and social norms on behavior, thus informing the design of interventions or campaigns that target attitudes, perceptions, and social influences to promote behavior change and adoption of healthy behaviors in diverse populations and contexts.
Health Action Process Approach	The Health Action Process Approach (HAPA) is a dual-phase model that explores the processes involved in behavior change, from motivation to action and maintenance. Similar to the Theory of Planned Behavior (TPB), HAPA examines individuals’ intentions, motivation, and self-regulatory processes in promoting behavior change. HAPA distinguishes between the motivational phase (intention formation) and the volitional phase (action initiation and maintenance) and identifies self-efficacy, outcome expectancies, and action planning as key determinants of behavior change. By understanding the stages and processes involved in behavior change, HAPA provides a framework for designing interventions that target both motivational and volitional factors to support behavior change across different stages.	When designing behavior change interventions or programs, applying the Health Action Process Approach to address both motivational and volitional factors involved in behavior change, thus providing support for individuals in forming intentions, planning actions, and maintaining behavior change over time, and increasing the effectiveness of interventions in promoting sustained behavior change across various populations and behaviors.
Information-Motivation-Behavioral Skills Model	The Information-Motivation-Behavioral Skills (IMB) Model integrates cognitive and motivational factors in predicting health behavior change. Similar to the Theory of Planned Behavior (TPB), the IMB Model examines individuals’ attitudes, intentions, and behavioral skills in promoting behavior change. The IMB Model emphasizes the importance of information, motivation, and behavioral skills in facilitating behavior change and reducing risky behaviors. By addressing knowledge gaps, enhancing motivation, and building behavioral skills, the IMB Model provides a framework for designing comprehensive interventions to promote health behavior change.	When developing health promotion interventions or education programs, applying the Information-Motivation-Behavioral Skills Model to assess individuals’ knowledge, motivation, and behavioral skills related to health behaviors, thus designing interventions that provide information, enhance motivation, and build skills to support behavior change and reduce health risks in diverse populations and settings.