I’ll start with a very simple question. One that we have all asked ourselves at some point: What makes behaviors more and less easy to modify or even eliminate?

Readers will think of examples of acquaintances, or even themselves, who have been able to modify behaviors that seem impossible for others to change, such as stopping biting their nails, quitting smoking, or resisting compulsive shopping.

Behavioral Momentum Theory: What Is It Exactly?

Here comes into play one of the proposals to respond to our concern: the Theory of the Behavioral Moment by John Anthony Nevin (1988) , but first, we will explain some basic concepts of the Psychology of Learning to put the mind at ease.

  • Learning : Is the conscious or unconscious acquisition of knowledge and/or skills through study or practice. It can also be defined as a relatively permanent change in behaviour due to reinforcement.
  • Reinforcer : Any element that increases the probability of a behavior being repeated. (For example, giving a treat to our pet when he responds to a command we have given him will cause him to do it again in the future)
  • Continuous reinforcement : Consists in granting a booster whenever the desired behaviour is emitted.
  • Partial reinforcement : Consists in giving the reinforcer sometimes yes, sometimes no to the same behaviour. It can be established in every 5 correct answers (Fixed) or at random (Variable) so that a booster could be given in behaviour number 3, and in the following one in behaviour number 15 without there being a fixed number.
  • Extinction : This is the name given to the abandonment of reinforcement in order to eliminate a behaviour that was produced thanks to it.

With these terms in mind, we can begin to describe Nevin’s Theory of Behavioral Moment, or TMC from here on.

Explaining resistance to change

Nevin proposed the Behavioral Momentum Theory to explain the resistance to change of behaviors that, in many people, become automatic either by training or by a massive practice of them. Therefore, he proposed a concept: The behavioral moment , defined as the susceptibility of a behavior to be interrupted.

But what creates this susceptibility? What makes one behavior more resistant than another when it comes to eliminating it? The answer is found (among others) in the forms of reinforcement with which the behaviour was acquired .

Research supporting this theory

Let’s think of two mice we’ve trained to press a lever. Every time they did that, they’d get a food ball. The behavior is to push the lever, and the booster is to push the food pellet.

Mouse 1 has always been reinforced after pressing the lever, while mouse 2 has been partially reinforced (sometimes yes, sometimes no and without a fixed pattern). At this moment, when the behaviour is fixed, we want to eliminate it in our small rodents. Therefore, we stop dispensing food pellets every time the lever is pressed (extinction of the behaviour).

I ask you, dear readers: which mouse will take longer to extinguish its behavior, that is, to stop pressing the lever: the number 1 or the number 2?


Mouse number 1, which learned by continuous reinforcement, will very quickly extinguish the behavior because he will realize that no more food falls into his trough no matter how many times he presses the lever. In other words: if he was always given food and suddenly it is not given, he will make a few attempts that, after being failed, will be given up definitively.


And mouse number 2? It will suffer a paradoxical effect explained by the Frustration Theory (Amsel, 1962) by which its behavior will not only not start to extinguish immediately, but will increase.

Why does this happen? Mouse number 2 was reinforced sometimes yes, sometimes no. He doesn’t know when a ball will fall back into his feeder, but he knows that there must be a few lever strokes where it won’t fall and some where it will. So he will press the lever 20, 100, 200 times until he finally understands that there will be no more balls in the trough if he emits the behaviour and it ends up dying out.

Or what is the same: the number 1 mouse had less behavioral momentum than the number 2.

How does this phenomenon affect us in our lives?

If we divert our gaze from the mice to ourselves, this explains a multitude of everyday actions:

  • Look at the cell phone from time to time to see if we have messages or calls.
  • Refresh social networks in search of a Like.
  • Look frequently in the direction where we know a person is coming who has been waiting on the street for a long time.
  • Check the mailbox even on holidays (maybe the postman felt like working…) in case there are letters.

Disorders Affected

But it can be applied not only to such everyday behaviours, but also to disorders such as gambling, addictions, eating disorders… in which apparently there is a continuous “reinforcement”, but in reality this is not the case. A gambler doesn’t always manage to get money out of the machine, a cigarette produces instant pleasure, but it stimulates areas of the brain that ask for more and more, and more of the stimulus to satiate themselves, a person with binge eating disorder may fill up with food and be assailed by a great discomfort because of his lack of control that makes that “little pleasure” go away…

The difficulty of quitting an addiction or overcoming an eating disorder is well known, and therein lies the resistance to extinction of the behaviors that are emitted, in relation to how they were acquired.

Even with everything, it is necessary to make a prudent note. The Theory of the Behavioral Moment has given an excellent framework for the study of resistance to change and the extinction of behavior, but logically, the complexity that characterizes us, specifically, human beings, makes it unlikely that only the behavioral moment explains the extinction by itself. In any case, it is a very interesting theory to take into account for our knowledge.