I'm going to give you the ultimate guide to reasoned action theory, which is the world's foremost theory of persuasion and behavior change.
If you're a student and you read this, I can guarantee you'll do well on any test or homework assignment that involves this theory.
If you're a practitioner of persuasion of behavior change, this will make you more effective at your job.
Why Learn About Reasoned Action Theory?
One of the most common functions of communication is to change people's attitudes and to change people's behavior, what we commonly think of as persuasion.
Persuasion is important in almost every inter-personal and a business interaction where we have to try to influence people. It's ubiquitous. It happens all the time, and it's important to be able to be good at it.
There's one theory that dominates the modern scientific discussion of persuasion and behavior change, and that theory goes by a couple of different names, but it's still the same theory. It's called reasoned action theory or the theory of reasoned action or the theory of planned behavior. But it's all the same, and I'm going to describe it for you.
So why might you want to learn about the theory of reasoned action?
To understand the psychology of health behavior. First of all, you might want to change people's behaviors. I study health, so I'm often thinking about how do we get people to adopt healthy behaviors or stop unhealthy behaviors. This is an important topic that I teach to my students. That’s one reason you might want to learn it.
To understand the link between beliefs, attitudes, intentions and behavior. You might be interested in the underlying psychology of behavior change. That is how do attitudes and beliefs and intentions relate to behavior. This theory explains those connections.
To help you focus behavior change interventions. Finally, it might be your responsibility to change people's behavior in your job, to get them to buy something or to click on something or to start some behavior or to stop some behavior. This theory will help you target those persuasive efforts.
Terminology
Belief: probability that an ‘object’ has an ‘attribute’
Let's start with some general definitions of the main terms. One of the main terms, and the theory is a belief, and if you look at the slide here, a belief is the probability that an object has some attribute. In the context of the theory of reasoned action, it's normally the belief that some action or some behavior will lead to some consequence.
e.g. "I think if I eat donuts at every meal, I will gain weight." That's a belief about donuts.
Attitude: an evaluation of some object
Another key term in the theory is attitude, and attitude is an evaluation of some object. In our case, it's an evaluation of some behavior, and normally it's an evaluation of the consequences of a behavior.
e.g. "I believe that eating donuts at every meal is bad for me." That would be an attitude towards eating donuts.
I give a more technical definition in the slide from Fishbein & Ajzen, “a disposition to respond favorably or unfavorably towards some psychological object.” That's a textbook definition.
I think just the idea that an attitude is an evaluation of some behavior in this case. Is it good or bad? Is it helpful or harmful? Is a useful definition.
Intention: readiness to perform behavior; the subjective probability of performing some behavior
In technical academic discussions of the theory of reasoned action, you'll often see an equation that includes all of these terms. So I want to define each of these terms in turn.
Behavioral intention: your readiness to perform some particular behavior
Attitude: the evaluation of the behavior.
Subjective norm is whether I think other people want me to perform the behavior. Then there are the components of these things like beliefs, evaluations, normative belief, and motivation to comply. I want to describe each of those in more detail in turn.
Whenever you hear a discussion of the theory of reasoned action or the theory of planned behavior, it won't be long until you see a chart like the one I've put on the screen now.
Diagram of the Theory of Reasoned Action
This is from Fishbein and Ajzen. It is a typical diagram of the theory of reasoned action, or in this case the theory of planned behavior.
The diagram shows the links between the main components of the model, and you'll often see it diagrammed this way.
I'll explain each of these in a little bit more detail. But you can see from the model that:
Attitudes are a function of beliefs and evaluations of outcomes
Subjective norms are a function of normative beliefs
Motivation to comply and perceived behavioral control or self-efficacy is a function of control beliefs and the power of those control factors.
All those things, attitudes, norms, and perceived control lead to intentions, which is the readiness to do the behavior, and then the intentions lead (imperfectly) to behaviors.
That's the theory of reasoned action in a nutshell.
Here's the more detailed diagram of the same theory where you see what are the factors that actually lead to our beliefs.
The things like personal, demographic and environmental factors lead to our beliefs, which then in turn lead to our attitudes norms and so on, which leads to our intentions, which lead to behavior.
The theory of reasoned action is actually a mathematical model. These are the equations that allow you to predict behavioral intentions (BI) as a function of attitudes and subjective norms.
Theory of Reasoned Action (Behavioral Intention):
Theory of Planned Behavior (Attitudes):
Intention:
Salient Outcomes:
Which outcomes are actually important to a person engaging in a particular behavior? If you're thinking about the behavior of going on a diet, the important outcomes might be things like health outcomes, appearance outcomes, difficulty, or costs. These might be the salient or important or relevant outcomes. When we think about subjective norms, that's what we think other people want us to do.
Important Others:
In addition to thinking about salient outcomes, there's this idea of important others. In this theory we think about subjective norms, which is what we think other people want us to do.
“Well, I don't care about all other people. I care about important others.” When you think about the theory of reasoned action, you have to identify the important others who are likely to influence the behavior in question.
Behavior Under Volitional Control:
The theory of reasoned action or the theory of planned behavior, these are rational theories of volitional behavior, meaning behaviors we can do voluntarily. There are some behaviors which we might be coerced to do, or which are not under our control at all. This theory won't predict those behaviors. It predicts behaviors that we either do or don't do voluntarily.
Behavioral Intention (BI)
Let's start with the highest level equation in this theory. It says that behavioral intentions are a function of attitudes and subjective norms.
We already know behavioral intention is our readiness to do a behavior. Attitude is our evaluation of the outcomes of the behavior really, and subjective norms are what I think other people want me to do.
I'll simplify even more.
Attitudes (A): our positive or negative evaluation of the behavior in question.
“Do I think the behavior is a good idea? Do I think the behavior will lead to outcomes that I personally value?” That's my attitude towards the behavior.
For thinking about predicting someone's intention to exercise, their attitude towards exercise is a function of all their beliefs about whether exercise will lead to outcomes that they desire. If a person thinks exercise will lead to a lot of outcomes that they desire, the person has a positive attitude towards exercise. If they think that exercise will lead to a lot of outcomes that they don't like, then they will have a negative attitude towards exercise.
Subjective Norms (SN): the sum across all of the important people in our life and whether we think those people want us to do the behavior.
When it comes to exercise, we might think, “Does my partner want me to exercise? Does my doctor want me to exercise? Does my mother want me to exercise? Do my friends want me to exercise?” The sum of all those is the subjective norms.
Think of this in very simple terms. Our intentions are a function of attitude, “Do I think the behavior is a good idea”? and subjective norms, “Do I think others who are important to me think the behavior is a good idea”? It's a very simple, intuitive theory when you think of it that way.
Attitudes
This mathematical function says, attitudes (A) equals the sum of belief strength (b) times outcome evaluation (e) for each of our beliefs.
Beliefs (b): When we think about a behavior like exercise, I may have many beliefs about exercise. Something like, “I believe exercise makes me sweaty / is expensive / leads to injury / causes weight loss / will make me look better in my clothes / will allow me to sleep better.”
All of these are beliefs that I might have of exercise.
For each of these beliefs, there's a strength associated with this belief, and you can think of that strength being, “I'm certain that this behavior will lead to this outcome,” or “I'm certain that it won't lead to the outcome.”
We can think of there being a strength associated with each belief. So I can say, “I'm certain that if I exercise, I will be healthier. For that I have a high degree of certainty.” Another one might be, “I believe that exercise leads to injury. Well, I'm much less certain about that. I have a lower belief strength.” Belief strength is the certainty of the belief that some action will lead to some outcome.
Outcome Evaluation (e): “The outcome in question, is it something I like or dislike?”
Sticking with our exercise example, “I believe exercise will make me healthier. That's an outcome I value.“ Or maybe, “I believe that exercise will cause me to lose weight. That's an outcome I value.” On the other hand, “I believe exercise will lead to injury. That's an outcome I don't value.”
Multiply our belief strength (certainty) by our outcome evaluation (whether I like it or not) to see whether the outcome evaluation (e) has like a positive or a negative value.
Positive = I like the outcome
Negative = I don't like the outcome
Multiply the strength (certainty) by your preference (do you like the outcome or not?). If you do that across all of the beliefs and you sum that up, mathematically you arrive at a computation of your attitudes score for a particular behavior.
Subjective Norms
Subjective norms are the sum of the product of normative beliefs and motivations to comply, across each important other.
In the previous equation, we were summing across every belief. In this equation, we're summing across each important other person in our life with respect to this behavior.
When I think about exercising and whether I should or I shouldn't, I think about my friends, my partner, my children, my parents, my doctor, my exercise coach. These are the people who I might think whose opinions matter to me when it comes to exercise. They are the important others in my life.
For each of these people, I will have two psychological values.
Normative Belief (NB): Let's imagine my doctor as an important other. “Do I believe my doctor wants me to exercise?”
That's my normative belief, and you can imagine it ranging on a scale from +3 to -3. The +3 means, "I'm certain that my doctor wants me to exercise," and -3 is, "I'm certain my doctor doesn't want me to exercise."
My normative belief for each important other is just, “Do I think that person wants me to do the behavior in question? Do I think my mother wants me to exercise? Do I think my kids want me to exercise? Do I think my friends want me to exercise?” For each of those, I'll have a value on this continuum.
Motivation to Comply (MC): This is, “How much do I want to do what this person wants me to do?” I've already said who the important others in my life, so generally, these are people whose opinions I value or influence me, but to a greater or lesser extent.
Again, I go through the list of important others and I ask myself, “When it comes to exercise, how much do I want to do what my doctor wants me to do? How much do I want to do what my mother wants me to do? How much do I want to do what my children want me to do? What my friends want me to do? What my partner wants me to do?”
Then we take the product: Normative belief, that's on a scale of +3 to -3, “Do I think my doctor wants me to exercise?” Motivation to comply, on a scale of +3 to -3, “How much do I want to do what my doctor wants me to do?” I multiply those and repeat for every important other person. I sum them up, and that gives me the numerical value for subjective norms.
Types of Subjective Norms
One digression on subjective norms in the scientific literature says there are two kinds of norms. There are injunctive norms and descriptive norms.
Injunctive norms: what I think other people think I should do. So that's why I feel an injunction to do these things, because I think other people think I should eat kale. Other people think I should wear my seatbelt, wear a bike helmet, put batteries in my smoke detector, wear a mask, etc. That's an injunctive norm. My sense of what other people think I should do.
Descriptive norms: my perception of what other people think I should do, though the truth may be different. So descriptive norms are what I think most people do.
If I look at something like wearing masks, my injunctive norm says to me, "I think most experts want me to wear a mask. My doctor would want me to wear a mask. Maybe the people I care about want me to wear a mask. The public health experts want me to wear a mask." So my injunctive norm is definitely, "People think I should wear a mask."
The descriptive norm is my belief about what other people actually do, not what they say I should do. So I look out at the world and say, "Are people wearing masks?" If not very many people are wearing masks, then I have a descriptive norm that says, "Ah, most people aren't doing it," and that influences my decision about whether I should do it.
Two kinds of subjective norms: injunctive and descriptive.
The Intention-Behavior Link
Another part of the theory is the link between intention and behavior. Normally, the link between intention and behavior is very strong. For example, if you ask people their voting intention in the month before an election, it's a very, very, very good predictor of their actual voting behavior. The same goes for many consumer behaviors and other kinds of personal and healthy behaviors.
Intentions are generally strongly correlated with behaviors, but not perfectly. Our intentions can change between the time someone asks us about our intentions and the time we do the behavior.
In other instances, our intentions may be measured incorrectly. Someone can ask us a sloppy question about our intention in a research setting and therefore it's not well correlated with our behavior.
Volitional Control
Sometimes the behavior is not under volitional control. I occasionally ask my students, "How many of you intend to get an A in my class?" Well, they might all raise their hands, but the ultimate decision is up to me. They can decide how much they study and stuff like that, but they don't actually do the grading.
Another way of thinking about a behavior that's not under your volitional control is if I asked you, "Do you intend to be married within the next five years?" Well, you can intend to, but it takes two people to get married. So it's not completely under your control.
Theory of Planned Behavior
There's one important difference between the theory of reasoned action, which came first, and the theory of planned behavior, which is the more modern, current version of the theory.
The difference is the addition of this idea of ‘perceived behavioral control.’ You can think of as self-efficacy, or the belief that “I'm actually capable of doing the behavior in question,” such as exercise.
There is a mathematical function of perceived behavioral control in the model and it's very much like the other two. It's a function of two things; control beliefs and power of control factors.
Control beliefs: beliefs about whether certain things will be an obstacle. For example, control beliefs about my exercising might be, "I believe you need expensive equipment / to be in great shape already / professional guidance / to be flexible / a lot of time in order to exercise." Any of those beliefs about exercise influence the extent to which I think exercising is within my control.
Power of control factors: This is a measure of how powerful this factor is in either stopping me from doing the behavior or enabling me to do the behavior. If I think that you need expensive equipment to exercise and without it you can't exercise at all, then I think that factor has lots of power.
I multiply those factors and I sum those up across all the control factors. This summed value gives me perceived behavioral control, and you just add that into the model along with attitudes and subjective norms. This allows you to account for some behaviors, which are not completely under volitional control.
Example: if you're examining whether people want to eat fresh fruits and vegetables, there are many people in the United States, for example, where fresh fruits and vegetables are not easily accessible to them. They live in a food desert, fresh fruits and vegetables are too expensive, or they live in a situation, like a dormitory or with their parents and they don't get to shop for the groceries. The food selections are not under their control.
When you add perceived behavioral control, you can still use the theory of planned behavior to predict intentions of behavior, even though the behavior is perfectly under volitional control.
Summary
If you want to know how to use this theory to actually do persuasion and influence other people, I've done other videos that explain how you use each of these factors to design more persuasive messages and which persuasive strategies have the most evidence for being effective.
In summary, this is the theory of reasoned action or the theory of planned behavior. It's basically the same thing with the addition of these control factors.
Behaviors: linked to our intentions.
Intention: the immediate precursor to our behavior is our intention, that is our readiness to do the behavior. Intentions themselves are like the attitudes and subjective norms and control beliefs.
Attitudes: a function of the probability of certain outcomes and whether we prefer or don't prefer those outcomes, whether we positively or negatively value those outcomes.
Subjective norms: linked to normative beliefs, that's my beliefs about what I think other people want me to do and my motivation to comply with those other people. “How badly do I want to do what those people want me to do?”
Control beliefs: a function of what factors influence my ability to do this behavior and how powerful is each of those factors?
All those things sum up to influence intentions and then intentions influence behavior.
Although it looks really complicated and the mathematical formulas scare a lot of people who are encountering this theory for the first time, it's actually extremely intuitive.
Whether I'm going to do a behavior depends on whether I think it will lead to good outcomes, whether people who I trust and value think I should do the behavior, and whether I think I'm actually capable of doing the behavior. Those three things influence my attention to do the behavior, and then my intention normally leads to the behavior itself.
So there you have it, the theory of reasoned action and the theory of plant behavior. If you've got homework or a test about this or you’re a practitioner trying to persuade people, this is a really useful theory. It's the most evidence-based theory of persuasion of behavior change.
If you go to PubMed or you go to Google Scholar, you will find literally thousands of papers. They use these theories to predict every conceivable behavior, especially health behaviors, but also voting behaviors and every other kind of consumer behavior. I hope you liked it.