Discriminative stimulus: what is it and how does it explain human behavior?

Let us see what the discriminative stimulus is according to psychology and how it is used in functional analysis.

There are many concepts coming from behaviorism and behavior analysis.

We have heard about operant response, punishments and rewards, positive and negative reinforcers... but there are certain concepts that are less known despite the fact that they allude to phenomena that occur on a daily basis.

The behavioral concept we are going to talk about today is the discriminative stimulus.The behavioral concept we are going to talk about today is the discriminative stimulus, which we can say that it is the one that acts as an "energy" that acts as a warning signal that if something is done there will be consequences. Let's see a little in more detail what it is about.

What is a discriminative stimulus?

In behavior analysis, a discriminative stimulus is any form of stimulation that acquires the property of signaling to a subject, be it a person or an animal, that a given behavior that it may perform will imply a consequence, which can be positive (reward) or negative (punishment)..

Thus we say that something is a discriminative stimulus because it implies a form of "energy" that affects the subject (being a stimulus) and its presence manages to differentiate a response, making it more or less probable depending on the case.

As we have just commented, the role of the discriminative stimulus is to signal that if a certain behavior is presented, a certain consequence will be received. This should not be understood as meaning that the discriminative stimulus is the one that generates the response, but simply "warns" that if a behavior is performed there will be a consequence, both reinforcing and punitive. In other words, the discriminative stimulus is the signal that informs us of the availability of a consequent..

Functional analysis with discriminative stimulus

Let's understand this idea better with the case of Pedro, a store worker. Pedro is in charge of the cash register, but he has also been assigned other tasks that he does not like, such as sorting the clothes, folding them, and checking if there is any garment in bad condition. One day Pedro goes to his boss and complains about the tasks he has to do. The boss, instead of helping him, scolds him for his complaints and tells him that this is his job and that if he doesn't like it he can leave. Since then Pedro, when his boss is around, does not dare to complain for fear of being fired.

If we make a quick functional analysis we can identify three points here:

• Operant response: not to complain
• Discriminative stimulus: presence of the boss.
• Consequent: not to receive a reprimand.

If Pedro complains again when he is in front of his boss, he is likely to be reprimanded by him for his comments and may even be fired. As a result of all this, Pedro stops complaining when his boss is nearby, which effectively implies that the possibility of Pedro performing the behavior in question, complaining, when his boss is in front of him, who acts as a discriminative stimulus, has been reduced.

As we have commented the discriminative stimulus does not imply a consequence, but it is the signal that this consequence will happen if the behavior is performed. That is, the presence of the boss does not mean that Peter will be scolded or fired, but rather that it serves as a warning signal for him not to behave in a way that his boss does not like and that will result in a reprimand or the loss of his job.

On the other hand, if Peter is away from work with his colleagues in a bar and he knows that they don't like his boss either, we have a different situation. Here Peter will feel freer and will have no qualms about complaining about both his work and his boss. He complains and complains again and his colleagues support him, reinforcing his behavior even more and making Pedro keep on complaining until he lets off steam. Here the discriminative stimulus is the peers..

• Operant response: complaining
• Discriminative stimulus: presence of peers.
• Consequent: to receive support.

In other words, if Pedro complains about his boss in front of his colleagues while he is away from work, he will receive their support as a consequence and, therefore, this behavior will be reinforced.

Other examples

There are countless other examples that help us to understand the idea of the discriminative stimulus in greater depth.

For example, let's imagine that we go outside and we see that the sky is cloudy (ED1) and we feel a little cold (ED2).. Because of this we decide to go back inside the house, take an umbrella (RO1) and put on our jacket (RO2), so in case it rains we will not get wet (C1) and we will not be cold (C2). That is, if the sky is cloudy and it is cold, it increases the chances that we take an umbrella and get warm and, as a consequence, we avoid getting cold and wet.

Another case is the typical scene of a mother taking her son to a psychologist because the school has complained that he is misbehaving. She tells the professional that at home he behaves well, that he does absolutely nothing wrong, but that at school they say he is a real Pain in the ass. What actually happens is that the child, if he misbehaves at home in the presence of his mother (ED) she will punish him very severely (C), and therefore chooses to behave well at home (RO).

Relationship with the delta stimulus

In functional analysis there is another concept that is related to the discriminative stimulus, but in a sense that could be said to be the opposite: the delta stimulus.. This type of stimulus informs us of the unavailability of a consequent to a given behavior, neither positive nor negative.

Relating it to the case of Peter, if he is alone in the bathroom and knows that no one will hear him, he complains loudly about his boss. In this case nobody scolds him for his complaints, but neither does he support him, he receives absolutely nothing as a consequence of his criticism.

Thus, we can see the difference between the discriminative stimulus and the delta stimulus. In the case of the discriminative stimulus, there is a consequence that influences the subject's behavior, increasing or reducing it depending on whether he receives a reward or a punishment for committing it. On the other hand, in the delta stimulus there is no consequence that influences the subject's behavior, in the delta stimulus there is no consequence whatsoever, directly serving as a signal that whether the behavior is performed or not, there will be no reward or punishment for it..

The union of both types of stimuli can be seen in a classic experiment with rats. Let's imagine that we have one of these little animals in a cage where there are two lights: one green and the other red. When the green light is turned on (ED), if the rat presses a lever (RO), a piece of feed (C) will be dispensed. So, when the animal associates pressing the lever while the green light is on with receiving food, it is quite likely that it will press the lever every time that light comes on.

But what happens when the red light is on? In this case the animal does not receive food, whether it presses the lever or not. In other words, the red light on acts as a delta stimulus, a signal that nothing will happen after that stimulus is presented, no matter how hard the animal presses the lever.no matter how hard the animal presses the lever again and again. Thus, as the red light is turned on as many times, the animal will associate that it is useless to press the lever in that case, extinguishing this behavior over time because there is neither positive nor negative reinforcement.

Bibliographical references:

• Domjan, M. (2010). Basic principles of learning and behavior. Madrid: Thomson.
• Labrador, F. J. (2008). Técnicas de modificación de conducta. Madrid: Pirámide.