Theory of Planned Behavior

The theory of planned behavior (TPB) is a cognitive theory by Azjen (1985) that proposes that an individual’s decision to engage in a specific behavior, such as gambling or stopping gambling, can be predicated by their intention to engage in that behavior.

In This Article:

Behavioral intentions

The central premise of the TPB is that human behavior is most proximally and directly determined by a person’s behavioral intentions.

Behavioral intention represents a person’s readiness to perform a given behavior. It acts as a cognitive predisposition: a mental state that precedes the physical act.

This construct indicates how much effort an individual plans to exert. Generally, stronger intentions lead to a higher probability of behavior execution.

According to TPB, intentions are determined by three variables:

1. Specific Attitudes Toward the Behavior

Attitude toward the behavior constitutes the first major pillar of the TPB framework.

It reflects the degree to which a person has a favorable or unfavorable evaluation of the behavior in question.

This evaluation stems from behavioral beliefs, which are the perceived consequences of an action. For example, a student may believe that studying daily leads to high grades.

If they value high grades, they develop a positive attitude toward studying. Specificity is vital here. General attitudes rarely predict specific actions.

Only attitudes toward a precise behavior at a specific time reliably forecast outcomes.

2. Subjective norms

Subjective norms represent the second pillar, focusing on perceived social pressure.

This component captures how an individual believes significant others will view their performance of a behavior.

Significant others include influential figures like parents, peers, or medical professionals. These norms arise from normative beliefs, which are expectations attributed to these important groups.

A person also considers their motivation to comply, which is the internal desire to meet those social expectations.

If a social circle values fitness, an individual feels higher pressure to exercise regularly.

3. Perceived behavioral control

Perceived Behavioral Control (PBC) refers to an individual’s perception of the ease or difficulty of performing a specific task.

This depends on our perception of internal factors, such as our own ability and determination, and external factors, such as the resources and support available to us.

The theory argues that our perception of behavioral control has two effects:

It affects our intentions to behave in a certain way, i.e., the more control we think we have over our behavior, the stronger our intention to perform it.

It also affects our behavior directly; if we perceive that we have a high level of control, we will try harder and longer to succeed.

PBC is conceptually similar to self-efficacy, which is the belief in one’s own competence to succeed in a situation.

The theory of planned behavior is an extension of the theory of reasoned action (Ajzen & Fishbein, 1980; Fishbein & Ajzen, 1975)

According to the theory of planned behavior, perceived behavioral control, together with behavioral intention, can be used directly to predict behavioral achievement.

Examples

Here are some examples of how the three factors of the Theory of Planned Behavior (TPB) operate in real-world decision-making:

1. Specific Attitudes Toward the Behavior

This factor involves an individual’s evaluation of a specific action and their beliefs about its consequences.

Quitting Smoking:

An individual might hold a positive outcome expectancy, believing that if they give up smoking, they will be healthier, have sweeter breath, save money, and find exercising easier.

They might also have a negative outcome expectancy, such as worrying they will gain weight if they quit.

Their overall attitude is determined by how much they value these specific outcomes, such as concluding, “It is important for me to be healthier”.

Using Birth Control:

A woman’s general attitude toward birth control is a poor predictor of her behavior.

However, her specific attitude toward using birth control pills during the next two years serves as a highly accurate predictor.

Healthy Eating:

A person might weigh the consequences of eating more nutritiously (e.g., feeling healthier) against negative feelings (e.g., feeling hungry, unsated, or experiencing sugar withdrawals) to form an attitude about changing their diet.

2. Subjective Norms

This factor is driven by the perceived social pressure from significant others and the individual’s motivation to comply with those expectations.

Attending a Concert:

A person named Deepa might have a negative attitude toward classical music and ordinarily wouldn’t attend a violin concert.

However, if her best friend is playing in the concert, Deepa may believe her friend will be highly disappointed and insulted if she doesn’t show up.

This strong subjective norm overrides her personal attitude, making it highly likely she will attend.

Dieting:

A person might hold a negative attitude toward dieting (e.g., “I don’t really like dieting”) but still form a positive intention to change their eating habits because all of their friends eat healthily and they want to fit in and be more like them.

Quitting Smoking:

A smoker might feel immense pressure from their family and friends who strongly want them to quit, combined with their own internal motivation to please their loved ones.

3. Perceived Behavioral Control (PBC)

This refers to a person’s confidence in their ability to overcome barriers and successfully execute the behavior.

Quitting Smoking:

If an individual believes it will be easy to avoid smoking even when they go out to a pub in the evening, they have high perceived behavioral control.

Conversely, if someone believes they are completely unable to quit—perhaps due to several failed attempts in the past—their perceived behavioral control is low, and they likely will not even form an intention to try.

Dieting:

A person might genuinely intend to change their diet because they believe they have the willpower to do it.

However, if the purchasing and preparation of their food are actually controlled by someone else in their household, their actual control is low, making the behavioral change unlikely despite their intentions.

Everyday Tasks vs. Difficult Habits:

A person will form a strong behavioral intention for a task they perceive as easy, such as remembering to buy milk on the way home from work.

They will form a much weaker intention for a task they perceive as difficult or demanding, such as consistently remembering to use a condom during sexual intercourse.

Interventions

Health Interventions

Implementation intentions have proven particularly effective in health contexts.

Women instructed to form a specific plan detailing exactly when and where they would perform a breast self-examination showed significantly higher rates of actually completing the exam than those who held only a general intention to do so.

The same principle has been shown to meaningfully enhance outcomes in weight loss programmes and smoking cessation efforts.

Pro-Environmental Behaviour

Environmental behaviour follows a similar pattern.

In one workplace study, employees who were asked to write down and mentally visualise precisely when, where, and how they would recycle their plastic cups recycled nearly four times as many cups as a control group that made no such plans, a substantial effect from a minimal intervention.

Civic Engagement

Implementation intentions have also proven effective in voter mobilisation.

Prompting people to articulate a concrete voting plan, specifying what time they would go, where they would be coming from, and how they would get to the polling station, more than doubled the effectiveness

Smoking and Alcohol Use

TPB is the most widely used model in health psychology, and has proven particularly useful in predicting intentions related to smoking and alcohol consumption.

Hagger et al. (2011) found that all three components of the model, personal attitudes, subjective norms, and perceived behavioural control, correlated with alcohol-dependent individuals’ intentions to limit or stop drinking.

Crucially, those intentions also predicted actual behaviour, with the model accurately forecasting the approximate number of units consumed at both one and three months. Its predictive power did have limits, however: it failed to account for binge drinking episodes.

Evidence for the role of perceived behavioural control is provided by Penny (1996), who found that smokers who had previously failed to quit were less likely to believe they could succeed and therefore less likely to attempt quitting again.

This illustrates how past experience shapes perceived control, which in turn shapes intention, precisely as TPB predicts.

Automaticity and Resource Conservation

Implementation intentions facilitate “strategic automaticity,” which allows behaviors to occur without conscious deliberation.

Automaticity refers to the ability to perform actions quickly and without intense mental focus. Because the decision is made in advance, the individual avoids the “action initiation” struggle.

They do not need to rely on dwindling reserves of willpower or self-control. The situational cue triggers the behavior directly.

This mechanism bypasses common barriers like forgetfulness, procrastination, or competing distractions.

Consequently, the behavior becomes more resilient to stressful or busy environments.

Critical Evaluation

While the Theory of Planned Behavior (TPB) is one of the most widely applied social cognition models for understanding deliberative human actions, a critical evaluation reveals several significant theoretical, methodological, and practical limitations.

1. The Intention-Behavior Gap

One of the most persistent criticisms of the TPB is its failure to consistently predict actual behavior, an issue widely referred to as the “intention-behavior gap”.

This gap describes the failure to translate strong intentions into actual actions.

People often intend to change habits but fail due to distractions or procrastination. To solve this, researchers advocate for implementation intentions.

Implementation Intentions

Implementation intentions close the gap by ensuring that the best-laid plans are tied to concrete situational triggers, transforming abstract desires into executable, automatic actions

Implementation intentions shift an individual from a motivational mindset to an action-oriented mindset.

These plans specify exactly when, where, and how a goal will be achieved. They utilize “if-then” logic to link situational cues to specific actions.

For instance, a person might plan to exercise immediately after work on Mondays. This specific plan makes the behavior more automatic when the trigger occurs.

2. Over-Reliance on Rationality and Cognitive Variables

The TPB is fundamentally a cognitive model derived from expected utility theory, which assumes that individuals are rational actors who systematically and logically weigh the implications and outcomes of their actions before making a decision.

Because it assumes a high degree of voluntary control and rational calculation, the TPB struggles to account for irrational, spontaneous, or emotionally driven decisions.

Furthermore, critics argue that the model places too much emphasis on perceived cognitive variables.

By focusing entirely on an individual’s “perceived” social norms and “perceived” behavioral control, the model effectively ignores observable social and environmental facts that exert real, objective influence on a person’s behavior regardless of their perception.

3. Omission of Key Predictive Variables

Because the TPB’s predictive power for actual behavior is notably lower than for intentions, researchers argue that the model is incomplete and needs to incorporate additional variables.

Critical omissions include:

Past Behavior: The TPB does not adequately consider an individual’s past behavior, despite evidence that past actions are often one of the strongest and most accurate predictors of future behavior.
Moral Norms: The TPB relies on subjective social norms, but many behaviors are driven by internal moral norms, particularly actions that directly affect others, such as condom use or drink driving.
Anticipatory Regret: The TPB lacks an emotional dimension. Research shows that anticipating the negative emotions or regret that might follow a decision (or a failure to act) significantly influences future intentions and behaviors.
Self-Identity: How individuals perceive and label themselves (e.g., viewing oneself as a “green consumer”) can influence their intentions above and beyond the core variables identified in the TPB.

4. Direction of Causality and Correlational Limitations

The TPB postulates a unidirectional flow: attitudes, subjective norms, and perceived behavioral control shape intentions, which in turn shape behavior.

However, critics point out that the model fails to acknowledge the potential bidirectional transaction between these variables, as actual behavior can reflexively shape and alter a person’s attitudes over time.

Furthermore, the vast majority of research supporting the TPB relies on cross-sectional or correlational data.

Because these studies simply measure the fit of the model against observed data, the direction of causality is ultimately only inferred, requiring more prospective longitudinal studies to untangle true cause-and-effect relationships.

5. Methodological Vulnerabilities

The methods used to test the TPB have inherent weaknesses.

Studies heavily rely on self-reported data (e.g., asking participants to report their condom use or dietary habits), which relies on the risky assumption that self-reported behavior is an accurate reflection of actual everyday behavior.

Additionally, TPB questionnaires are highly susceptible to ordering effects and demand characteristics.

Experiments have shown that simply muddling the order of the questions regarding threat, attitude, and normative beliefs significantly alters the intercorrelations between these variables.

This suggests that social desirability and the perceived importance of the topic can artificially inflate the model’s apparent validity.

6. Lack of Universality and Cultural Bias

Finally, the TPB is a highly generalized model intended to cover all kinds of health and social behaviors, but critics argue it is invalid to apply a “one-size-fits-all” framework.

Different factors are salient for different behaviors; for example, subjective norms may be highly predictive of smoking cessation, but largely irrelevant for vitamin intake.

Moreover, the TPB has been designed and tested almost exclusively within a Western cultural context.

The model’s emphasis on individual autonomy, personal attitudes, and perceived control reflects Western biases and may not universally apply to interdependent or collectivist cultures, highlighting the need for a more culturally relative approach to behavioral prediction.

Interaction of Nature and Nurture

Behavioral intentions result from a continuous interaction between biological endowment and environmental experience.

Psychology rejects the idea that behavior is determined by only one of these forces.

The Role of Nature

Nature provides the baseline physiological hardware for human motivations. Evolutionary adaptations guide certain innate drives, such as the intention to protect kin.

Temperament also influences behavioral style: the biologically based differences in emotional reactivity. These genetic factors establish a range of reaction for an individual’s potential.

The Role of Nurture

Nurture encompasses the social conditioning and learning experiences that shape specific plans. Through socialization, individuals learn the rules and moral codes of their culture.

Social Learning Theory suggests that we form intentions by observing rewarded models. Environments provide the specific context that triggers or suppresses biological predispositions.

Reciprocal Determinism

The relationship between biology and environment is bidirectional.

Reciprocal determinism suggests that individuals actively influence their surroundings while being shaped by them.

Niche-picking occurs when a person’s genetic traits lead them to seek specific environments. These environments then reinforce the individual’s initial behavioral intentions.

Empirical Evidence

Study 1: Breast Self-Examination (Orbell, Hodgkins, & Sheeran, 1997)

Aim: To investigate if implementation intentions increase the frequency of breast self-examinations (BSE).
Procedure: A group of 148 women was recruited for the study. Participants were randomly assigned to either a goal intention group or an implementation intention group. The latter group was asked to state exactly when and where they would perform the BSE.
Findings: Data showed that 64% of the implementation group performed the BSE. Only 14% of the control group completed the examination.
Conclusions: Specifying situational parameters significantly enhances the likelihood of following through with health-related behaviors.

Study 2: Pro-Environmental Behavior (Holland, Aarts, & Langendam, 2006)

Aim: To test if planning can increase recycling behavior in a workplace setting.
Procedure: Employees at a large organization were studied. One group was required to write down exactly when and how they would recycle their plastic cups. A control group received only general information about the benefits of recycling.
Findings: The group with specific plans recycled four times as many cups as the control group. This effect remained consistent over several weeks.
Conclusions: Concrete planning creates a persistent behavioral change that far exceeds the impact of general motivation.

Study 3: Voter Mobilization (Nickerson & Rogers, 2010)

Aim: To determine if “making a plan” increases voter turnout during a primary election.
Procedure: Over 280,000 potential voters were contacted via phone. One group was asked standard mobilization questions. Another group was asked specific questions about their timing, location, and transportation to the polls.
Findings: The “implementation” phone calls were more than twice as effective. Turnout increased significantly among those who articulated a specific plan.
Conclusions: Strategic questioning that forces implementation planning is a highly effective tool for civic engagement.

How does TPB differ from the Theory of Reasoned Action?

The primary difference between the Theory of Planned Behaviour (TPB) and the Theory of Reasoned Action (TRA) is the addition of a third component, perceived behavioural control, to address behaviours that are not entirely under an individual’s voluntary control.

Limitations of the Theory of Reasoned Action (TRA)

The TRA, originally developed by Martin Fishbein and Icek Ajzen in the 1970s, assumes that human behaviour is goal-directed and driven by a person’s behavioural intention.

Under the TRA framework, this intention is shaped by only two factors:

Attitude towards the behaviour: An individual’s personal evaluation of the behaviour, based on their beliefs about the expected outcomes and consequences.
Subjective norms: The perceived social pressure from significant others (such as family and friends) regarding whether the behaviour is desirable or acceptable, combined with the individual’s motivation to comply with those expectations.

The central limitation of the TRA is its assumption that individuals are completely rational decision-makers and that their behaviour is entirely volitional—meaning it is strictly under their personal control.

Consequently, the TRA is inadequate for explaining situations where an individual strongly intends to perform an action but fails to do so because of environmental obstacles, a lack of resources, or addictive habits.

TPB’s Addition: Perceived Behavioural Control (PBC)

To overcome the TRA’s inability to account for non-volitional behaviours, Ajzen extended the model in 1985 to create the TPB by introducing perceived behavioural control (PBC).

PBC refers to an individual’s belief regarding how easy or difficult it is to successfully perform a specific behaviour, particularly when facing potential barriers.

This new component is fundamentally linked to Albert Bandura’s concept of self-efficacy—the belief in one’s capacity to exercise control over events and effectively execute actions.

By adding PBC, the TPB accounts for two critical types of control factors that the TRA ignores:

Internal control factors: The individual’s personal skills, abilities, and knowledge.
External control factors: Environmental obstacles, access to resources, and opportunities.

How the TPB Operates Differently

In the TPB framework, PBC interacts with attitudes and subjective norms to determine the strength of a person’s behavioural intention.

If a person believes a task is too difficult or completely outside their control, their intention to act will be weak, regardless of how positive their attitude is or how supportive their social network might be.

Furthermore, unlike attitudes and subjective norms, PBC is uniquely capable of bypassing intention entirely to exert a direct influence on actual behaviour.

If an individual’s perception of their control over a situation is accurate, this direct link helps explain why they might successfully execute a behaviour independently of their initial intentions.

Because the TPB incorporates this measure of personal control and past behaviour (which heavily influences a person’s confidence), it has generally proven much more successful than the TRA at predicting complex behaviours.

It is especially effective for predicting actions that require overcoming significant challenges, such as quitting smoking, adhering to an exercise regimen, or making dietary changes, where willpower alone is insufficient.

References

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Ajzen, 1., & Fishbein, M. (1969). The prediction of behavioral intentions in a choice situation. Journal of Experimental Social Psychology, 5, 400-416.

Ajzen, I., & Fishbein, M. (1970). The prediction of behavior from attitudinal and normative variables. Journal of Experimental Social Psychology, 6, 466-487.

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Ajzen, I., & Fishbein, M. (1980). Understanding attitudes and predicting social behavior. Englewood Cliffs, NJ: Prentice Hall.

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Gollwitzer, P. M. (1999). Implementation intentions: Strong effects of simple plans. American Psychologist, 54(7), 493–503.

Holland, R. W., Aarts, H., & Langendam, D. (2006). Breaking and creating habits on the working floor: A field-experiment on the power of implementation intentions. Journal of experimental social psychology, 42(6), 776-783.

Nickerson, D. W., & Rogers, T. (2010). Do you have a voting plan? Implementation intentions, planning prompts, and voter turnout. Psychological Science, 21(2), 194–199.

Orbell, S., Hodgkins, S., & Sheeran, P. (1997). Implementation intentions and the theory of planned behavior. Personality and social psychology bulletin, 23(9), 945-954.