The Science of Everything Podcast - Episode 28: Classical Conditioning

Episode Date: January 7, 2012

A discussion of classical conditioning, including an analysis of its key components of the conditioned and unconditioned stimuli and responses, the acquisition process, extinction, recovery, generalization, and discrimination. I also discuss some applications of classical conditioning to understand a wide variety of behaviors, including taste aversion, drug tolerance, sexual fetishes, and emotional responses.

You're listening to The Science of Everything podcast, episode 28. Classical Conditioning, and I'm your host, James Fodor. In this episode, I'm going to discuss classical conditioning, the oldest type of learning that is known about. In particular, I'll discuss the various elements of classical conditioning, including the conditioned and unconditioned responses and conditioned and unconditioned stimuli. I'll discuss some examples of classical conditioning

so that you can get a better understanding of how it works and what it is. I'll also go through some more specific, aspects of classical conditioning, including the process of acquisition, generalization and discrimination, and extinction and recovery. I'll also then talk about some applications of classical conditioning in practical and scholarly areas such as taste diversion and various biological factors that can be better understood using the model of classical conditioning. Just to note, I was originally going to do this podcast as a single episode, including the next episode on operand conditioning, a different type of learning.

but because it grew too long, I've decided to split them up, so there'll be a sort of a second part to this where I talk about operand conditioning and also a bit on observational learning. Okay, so let's start off with classical conditioning. First of all, I need to define what I mean by learning, or what psychologists mean by learning. Learning is generally defined as a relatively permanent change in behavior or knowledge that occurs as a result of experience.

So, key thing about learning there is that it has to be as a result of experience, not a change in behavior that results from maturation, example, or going through puberty or something like that. That is not considered learning, even though it results in a change of behavior. Okay, so now we'll start with classical conditioning. Classical conditioning is called classical conditioning, because it's the oldest type of conditioning known it was discovered and described in the literature first. The key thing to realize about classical conditioning, the important thing to understand, is that it requires a reflexive response, or some stimulus that gives rise to an automatic innate reflex that is governed by the autonomic

nervous system. So an innate reflex means that it happens automatically and without voluntary or conscious control. So an example for reflexes if you touch a hot stove, your hand automatically draws back. For a reflex like that, the information does not actually need to travel all the way to the brain. It's just processed in the spinal cord and then the information sent directly to the neurons that innovate the skeletal muscles to withdraw the hand away from the source of the heat. So the point there is that no conscious control is necessary or in most cases even possible to exert over the response. There's a stimulus, gives rise to an innate reflexive response. That is essential for classical conditioning to occur.

So without some source of innate reflexive response, you can't have classical conditioning. So the example, the canonical example, which initially led to the discovery of classical conditioning was salivation in anticipation of food, which I'll describe in a second. but there are many other examples of innate reflexes which can be used to generate classical conditioning. So some examples of these sorts of reflexes that you can harness include various aspects of the sexual response. Eye blinks solicited by puffs of air directed at the eye. Leged withdrawal from electric shock or indeed any withdrawal from electric shock. Electric shocks are pretty good at eliciting reflex responses. Various emotional reactions such as fear or excitement or anger as a result of various.

stimuli, and also associated physiological indicators of those emotions like skin conductivity, heart rate, and so on. There are also other ones that are only found in animals like reflexive pecking in certain birds, and also some birds have a reflexive response to move around eggs or objects that are shaped like eggs if they're placed near them. There's also gagging a nausea response, vomiting, coughing and things like that if objects are placed in the mouth or down the throat. So there are many, many different innate reflexive responses in humans and also in other animals which can be utilized in classical conditioning. So just bear that in mind as I'm describing the elements of classical conditioning. Given that we require an innate reflexive response, classical conditioning is basically the process of harnessing this innate response to a stimuli.

So you've got a stimuli and innate response which happens automatically. And what you do is you take some other stimuli, some random stimulus, it can be anything really, pair it with this initial stimulus that gives rise to the reflexive response. So, for example, pair it with the frightening situation that gives rise to the fear response or the puff of air in the eye or the food that gives rise to salvation. You pair the two stimuli together and then you present the second stimulus on its own without the initial stimulus and find that it gives rise to some response by itself without the presence of the initial stimulus.

that process of basically taking some initial neutral stimulus and then pairing it with the initial stimulus and then presenting the initially neutral stimulus by itself and then having that stimulus give rise to some response that process is called classical conditioning okay so that's the basic idea pair stimuli together then the initial neutral stimulus becomes a condition stimulus which gives rise to a response when previously it didn't so first of all i'll describe what pavlov did and then go through the elements of classical conditioning in more detail. Pavlov was actually, Ivan Pavlov was a Russian scientist in the late 19th, early 20th century. He was actually doing work on digestion and placing meat powder in dogs' mouths and measuring salvation as associated with that.

But what he discovered, really by accident, was that dogs began anticipating their meals, or specifically they began salivating in anticipation of their meals, that when the person who brought them their meat powder or their food entered the room, or even, I think, when they heard him coming, they began to salivate even before the meat was actually there. So Pavlov noticed this and thought it would be an interesting thing to study. So he set it up in a proper experiment format whereby Pavlov sounded a tone and then fed, that is a bell, and then he fed the dogs some meat powder and placed it in their mouths and measured the salivation that resulted. After a few repetitions of this, he found that the dogs began salivating immediately upon hearing the tone,

even before the meat powder had into the dog's mouth. So in this situation, the reflexive response is the salivation. The initial stimulus that gave rise to that was the meat powder, but the new stimulus was the ringing of the bell. And the conditioning occurred when the new stimulus was paired a few times with the old stimulus, and then was given by itself and still gave rise to the bell. to some response or some behaviour. That is, the animal had learned to associate the tone with the food and therefore they were salivating in response to that. That's the initial experiment that

generated this concept of classical conditioning. Now I'm going to go through the elements in a bit more detail so that you can really understand it, because it's a little bit hard to keep all the concepts together, first blush. Okay, so there's five key elements in classical conditioning. The neutral stimulus, the unconditioned stimulus, the conditioned stimulus, the unconditioned response, and the conditioned response. So this is generally abbreviated, like NS for neutral stimulus, US for unconditional stimulus and so on, if you see those written. Okay, the neutral stimulus is pretty easy to understand. That's just any event process, something happening, like in Pavlov's example, it was ringing the bell. Any event that does not cause an overt

behavioral response. So it's just some event that doesn't do anything by itself. Bringing the bell, for example. The unconditioned stimulus, the US, is a stimulus that automatically or naturally triggers a response without any previous requirements for learning or whatever. So this is the stimulus that generates the response by itself. So in the, in Pavlov's case, the unconditional stimulus was the meat powder. The meat powder by itself automatically triggered the unconditioned response. which is the reaction produced as the result of the unconditioned stimulus. So, unconditioned response, they're the two things that happen automatically that, well, the stimulus gives rise automatically to the unconditioned response.

Classical conditioning occurs when you pair the unconditioned stimulus with a neutral stimulus, which is just, remember, some other random stimulus that by itself doesn't do anything. You pair them together, and then you present the neutral stimulus just by itself. And what you'll find, if classical conditioning occurs, or is to occur, is that the neutral stimulus becomes the conditioned stimulus. So the neutral and condition stimulus are basically the same thing, except the condition stimulus is sort of what the neutral stimulus becomes after being paired with the unconditioned stimulus or after the conditioning has occurred. So neutral stimulus paired with unconditional stimulus, then the neutral stimulus is presented by itself. And if that gives rise to a response, when presented by itself, it's referred to it was the conditioned stimulus, because it's now a stimulus that's giving rise to a response, but as a result of conditioning, so it's the conditioned stimulus. Now, the response elicited by the conditioned stimulus is the conditioned response. Now, in Pavlov's example, remember, the neutral stimulus was initially the bell ringing, but that then became the

condition stimulus after it was paired with the provision of the meat powder. The conditioned response in Pavlov's case was exactly the same as the unconditioned response, that is, salivation. And that can often occur. Basically, that the response is the same when presented with the unconditioned stimulus or the conditioned stimulus in Pavlov's case, salivation. But they don't have to be the same, and that's the key thing, and we'll come to that in some later examples. The conditioned response, that is the response after conditioning, does not have to be the same as the unconditioned response. They can be different. Okay, so bear those concepts in mind. The unconditioned stimulus gives rise to the conditioned stimulus. You pair the neutral stimulus with the unconditioned stimulus for a while.

Then the neutral stimulus becomes the condition stimulus. You present the condition stimulus by itself, and it gives rise to the conditioned response, if conditioning occurs, of course. That whole process is called classical conditioning. Okay, now I just want to discuss a couple of other misperceptions of classical conditioning, if you have some familiarity with this or have heard of it before. One misperception is that you have to have repeated pairings of the neutral stimulus and the unconditioned stimulus in order for learning to occur.

That is sometimes true, but it's not essential. Often you have to have repeated pairings, but not always. Sometimes a single trial is enough for conditioning to occur. Examples include fear conditioning and taste aversion conditioning, which we'll talk about later on. So often you need repeated pairings, but not always. Sometimes one trial's enough. And the other misperception that I discussed before,

but I'll go over again, is that classical conditioning only applies in sort of limited circumstances. That's sort of true in that you have to have a reflex, but it's not limited in the sense that it's just salivational or sort of mundane things. There are many different types of reflexes that can be relevant to classical conditioning. For example, the startle reflex, emotional responses, taste aversions, the orienting reflex,

one that I didn't mention before, that makes you pay attention to new stimuli, like sort of noticing something when it just appears. So there are many, many reflex reactions that can be relevant or can be utilized in classical conditioning. So now what I want to do is go through some examples of classical conditioning, and I'll spell out exactly which are the condition responses, which are the uncondition and so on,

so that you can get the idea. Okay, so some of these will sound like somewhat odd situations, but just to give you the feel for it. Okay, so every time someone flushes a toilet in an apartment building, the shower becomes very hot and causes the person having a shower to jump back out of the water stream. Over time, the person begins to jump back automatically after hearing the flush before the water to temperature even actually changes. So in this case, the unconditioned stimulus is the hot water or the increased temperature of the shower water, and the unconditioned response is jumping aback, basically that reflex reaction jumping away from the very hot water.

The neutral stimulus is the sound of a flushing toilet. But over time, the neutral stimulus, the flushing toilet is paired with the hot shower, and the neutral stimulus becomes the conditioned stimulus, which then gives rise to the conditioned response of jumping away from the hot water. So in this case, as well, the conditioned and unconditioned response, responses are the same, jumping away from the hot water. Second example, you eat a new food and then become sick because of the flu or some viral infection. As a result, you develop a dislike for the food and become to feel nauseated whenever you smell the food and therefore don't want to eat it. That's called

taste aversion. Taste aversion, by the way, is a particularly common example of classical conditioning, and I'll talk about that a bit more detail later on. So in this case, the neutral stimulus was the smell or taste of the food. The unconditioned stimulus is basically the infection or the illness, the flu virus, whatever exactly, has caused you to become ill, and the unconditioned response is the feeling of nausea or sickness as a result. Therefore, the condition stimulus is the taste or smell of the food, and the conditioned response is feeling nauseous in response to smelling the food or tasting it. Once again, this is another example where the conditioned and unconditioned responses are basically the same thing, feeling nauseous.

Moving on to the third example, an individual receives frequent injections. of drugs, which are administered in a small examination room at a local clinic. The drug itself causes increased heart rate, but after several trips to the clinic, the individual begins to experience an increased heart rate simply by being in a small room. So in this case, the drugs themselves would be the unconditioned stimulus, and the unconditioned response would be the increased heart rate. The being located in a small room would be the neutral stimulus, which then becomes the condition stimulus upon pairing with the drug injections, and the condition's response would once again be the increased heart rate. On to the fourth example, this is a famous one from John Watson,

who conducted an experiment with a young boy, well, it was really a baby called Albert, in which he paired a white rat with a loud, startling noise. So after a few trials, Every time Albert the baby just saw the white rat, he began to cry because the loud noise had caused him to cry before, and now he had been conditioned to associate the rat with the loud noise. So in this case, the loud noise was the unconditioned stimulus, and the unconditioned response was Albert crying. The neutral stimulus, which then became the conditioned stimulus, was the white rat, the sight of the white rat. and the conditioned response was, again, Albert crying.

This case is quite famous, it's sort of referred to as Little Albert. I just wanted to point out that some of the claims it are made about Albert, like throughout his life having a fear of rats and rabbits or something like that, is exaggerated. Basically, there was no follow-up, no extinction, which I'll talk about in the second, of the conditioning, but also no real follow-up to, figure out if I was okay afterwards. So it's highly unlikely that one little experiment like this is going to have affected Albert throughout his life. We don't really know, but just be wary if you hear claims about Albert having a fear of rabbits or rats throughout his life. That's probably not true.

Okay, so that's some examples. Hopefully you now get the feel of what classical conditioning is. I now want to talk more about acquisition, that is, how the conditioning process actually occurs in the factors that can alter that. specifically refers to the training stage during which a neutral stimulus is transformed into a condition stimulus as a result of pairing with an unconditioned stimulus. Now the order and duration of the presentation of the neutral stimulus relative to the unconditioned stimulus determines how easily and how quickly conditioning occurs. Optimum conditioning occurs when the neutral stimulus is

presented first and then continues to be presented up until the unconditioned stimulus is presented. You can do it in lots of other ways as well. For example the neutral stimulus could be presented and then taken away and then present it again and then taken away before the unconditioned stimulus, or it could even occur, the neutral stimulus could occur after the unconditioned stimulus, or you could present the unusual stimulus and then have a substantial gap before presenting the unconditioned stimulus, but all of these variations result in slower and less intense conditioning. The reason for this is essentially, as has been discovered with more recent work on classical conditioning, is that what fundamentally drives

FIves position and therefore classical conditioning is the predictive value of the neutral stimulus in making a prediction or in indicating the impending presence of the unconditioned stimulus. So the better a predictor of the unconditioned stimulus, the neutral stimulus is, then the more likely and the more intense conditioning will be. That's why if the neutral stimulus occurs closer to the unconditioned stimulus, and if it occurs for a longer duration or more times, there'll be more intense conditioning. Similarly, the stronger the uncontentioned stimulus is, then the stronger the unconditional response will be, and therefore the stronger the conditioning will be.

So the more intense the stimuli and responses are, the more strongly conditioning will occur. Also, generally, the more pairings you have of the neutral stimulus with the unconditioned stimulus, the stronger will be the conditioned response. So basically, you want the, in order to get maximum conditioning and fastest than strongest conditioning to produce the most robust, strongest conditioned response, you want to present the unconditional, excuse me, the neutral stimulus, you want to present it as close in proximity and time to the unconditioned stimulus and present it, and repeat that many times over, and have the unconditioned stimulus and unconditional response being strong, stimuli, strong response

being very pertinent to the animal or human. There are a couple of other things to say about acquisition. One interesting phenomenon is referred to as blocking. Basically, what this means is that when an organism has been conditioned to a particular condition stimulus, neutral stimulus becomes a conditioned stimulus, presentation of a different neutral stimulus, along with the initial unconditioned stimulus

and then the condition stimulus, leads to much weaker conditioning of the second stimulus. So basically, if you have an unconditioned stimulus, then you condition, then you take neutral stimulus one, and condition that, and it becomes the conditioned stimulus. Then you take neutral stimulus two, so a new neutral stimulus, and try and condition that as well. It won't work, or doesn't work very well. Basically, because the organism already has a reliable predictor of the unconditioned stimulus, that being the first neutral stimulus, which became the condition stimulus, and so it doesn't need another one. So in effect, the first condition stimulus

blocks the acquisition of a second conditioned stimulus. Another phenomenon is referred to as overshadowing, kind of like blocking, except that it happens when two neutral stimuli are presented at the same time, as opposed to one after the other. In that case, if you present two neutral stimuli along with the unconditioned stimulus, what will happen is the stronger or more salient neutral stimulus will overshadow the weaker or less salient one, and therefore it will be conditioned. So, for example, if you give someone a substantial electric shock

and also a puff of air in their face, either of those alone could be conditioned and could become the conditioned stimulus, but because an electric shock is going to be more salient, stronger than a small puff of air, the electric shock would much more likely to be conditioned, therefore much more likely to become the condition stimulus than would the puff of air.

So that's overshadowing. Okay, there are a few other phenomenon that I wanted to talk about relevant to classical conditioning, generalization, discrimination, extinction, and recovery. So these are after the conditionings, has occurred after it's being acquired, these refer to basically what happens afterwards and some things you can do to play around with the conditioning process. So first of all, talk about generalization. Generalization refers to the phenomenon whereby the conditioned response occurs

when a stimulus, similar to, but not identical, to the condition stimulus is presented. So basically what's happening is the organism generalizes the learning or the conditioning to produce the conditioned response when stimuli, which are kind of like the original conditioned stimulus presented, but they're not quite the same. So, for example, it might be, experiments have been done where animals who are conditioned using a tone, that is a sound of a particular volume and pitch,

then we'll exhibit the conditioned response when presented with tones of different pitches and volumes. So they've generalized the learning to tones of other volumes and pitches. or durations as well, even though they weren't conditioned on those particular volumes and pictures of sounds. A similar thing could occur in terms of smells. Maybe you were conditioned with a particular smell, but smells sort of like that. Also elicit the unconditioned response. It could also be objects. For example, in the Little Albert case that I talked about before, he was conditioned to fear white rats by the presentation of the loud noise. But as far as I

remember, he generalized that conditioning to also have a fear of of small bunny rabbits because they look kind of similar. So that's a generalization. Discrimination is really just the opposite of generalization, which is the fact that if the organism experiences repeated exposure to a simulus stimuli that is not associated with the unconditioned stimulus, then the sort of false generalization is extinguished. It's discriminated between.

Extinguish just means that essentially that the conditioning goes away. I'll talk about that more in a second. So basically discrimination is the opposite of generalisation because generalisation means you apply conditioning of one condition stimulus or one neutral stimulus to another condition stimulus, which is kind of similar. Discrimination means that even though the two stimuli are similar, you distinguish one from the other, or you discriminate them. You will respond. You will produce the unconditioned response in response to the condition stimulus, but not, you will not produce the response when presented with a, similar neutral stimulus.

The key thing about discrimination is that even if there's an initial generalization, so suppose you have, you've got conditioned stimulus and then you present another neutral stimulus, which is similar to the condition stimulus, initially the condition response might be elicited. But over time, if the second neutral stimulus is repeatedly paired, excuse me, is repeatedly presented without the presence of the unconditioned stimulus, then eventually, the organism will discriminate between the condition stimulus and the second neutral stimulus, or the second condition stimulus,

and the second condition stimulus will be discriminated from the first, and therefore the response will cease. Because remember, it's all about predictive ability. If, say, if the white rat, to use the Little Albert case, predicts a loud noise, but the white bunny rabbit doesn't, then eventually the repeated exposure to the bunny rabbit without any loud noise will lead Albert to discriminate between seeing a white rat and seeing a bunny rabbit, as long as he has the visual system capable of making that distinction, of course,

because one predicts the loud noise, but the other one doesn't. And so that leads me on to extinction and recovery, which is really the reverse process. It's sort of unconditioning. Extinction refers to the fact that if the conditioned and unconditioned stimuli are not paired together for a number of trials, the organism will stop exhibiting the conditioned response. Because remember, it's all about predictive power. The condition response occurs because the organism is expecting that the conditioned stimuli will occur before or occur with the unconditioned stimuli.

The condition stimulus acts as a predictor for the unconditioned stimulus. In the case of Pavlov's dogs, the conditioned stimulus of the bells ringing acted as a predictor for the unconditioned stimulus of the food. But if you presented bells, if you rung the bells many times without presenting food, you're presenting the conditioned stimulus without the uncondition stimulus. And so eventually the conditioned response will stop, the dogs will stop salivating, because the condition stimulus is no longer predictive. The bells are no longer predictive of food being brought. And so once an organism stops exhibiting the conditioned response, that's referred to as extinction.

The initial conditioning has been made extinct. Now recovery is sort of a corollary of extinction. It is an interesting finding that, so suppose you condition a dog to salivate in response to bells, and then you extinguish it, you make that conditioning extinct on one particular day, then you come back the next day. It turns out that the conditioning or the conditioned response will spontaneously reappear again. This is called spontaneous recovery, though it's generally somewhat weaker. The response is not as intense or not as likely as it was before.

And then what you do with, then suppose you present the conditioned stimulus without the unconditioned stimulus, you present the bells without the food, and once again it caused the extinction of the conditioned response. then you come back the next day, and once again, you'll generally have spontaneous recovery, although once again, the condition response will be somewhat weaker. And basically, in order to have permanent extinction, what you have to do is continually extinguish it through a certain number of times, on a certain number of occasions, until spontaneous recovery no longer occurs. So that's an interesting phenomenon that extinction generally takes multiple times to occur.

It's not just a single one time. and that can be particularly relevant for some applications of classical conditioning, such as those that I'll talk about now, for example, taste aversion. Taste aversion is a very important and common application of classical conditioning. Basically, it's very common in humans, by the way, which is why it's such an important application, but also many other animals. Taste aversion occurs basically when humans, we'll talk about humans, but it can be other animals too, because when humans become classically conditioned to being averse to consuming certain types of food until extinction occurs, if ever. And the key thing about taste aversion is that it's a type of classical conditioning that can occur after only a single trial. So basically, if you eat a certain type of food and then become sick afterwards,

regardless of whether that sickness was actually caused by the food or not, you can often develop an aversion to that type of food that is feel sick if you eat it or even feel sick at the thought or smell of it. it. Just after a single trial, that is a single pairing of the unconditioned stimulus, which is whatever actually caused you to be sick, and the condition stimulus, which is the food, both producing the response of feeling ill. This is what I talked about before when I gave the taste diversion example of classical conditioning. So it's been shown that even something really obvious, like riding a roller coaster, I mean, that's going to make you feel sick for many people. If you eat a new type of food, say sushi before you go on the roller coaster, then it could

well be, it's quite likely that the thought of sushi or the taste of sushi or the smell of sushi will make you feel sick the next time. Because essentially what's happened is subconsciously you've paired the eating sushi with feeling sick afterwards. Even though you know you've been on a roller coaster and that's actually most likely what made you sick, not the sushi, it doesn't matter, you can still be conditioned to feel ill even at the thought of the sushi because that unconditioned stimulus of the roller coaster was associated with the conditions, well, the neutral and then became the condition stimulus of the sushi, both of which caused the response of feeling ill, feeling nauseous.

And so taste aversion is a common problem with certain medical conditions, for example, chemotherapy, because the chemicals that are being provided, essentially to kill the cancer, make the patient feel nauseous, make you feel very sick. And so whatever the patient is

eating at the time, or before, during their treatment, will be paired with that feeling of nauseous, of nausea, and what can happen is that the chemotherapy patients can actually go off their food, not just a particular type of food, but all types of food, even the thought of eating makes them sick.

Now, it takes the version that happens more readily to new foods or unknown foods than to existing foods, but it can happen to any type of food, really. And once again, the key thing about it is that it can happen after a single trial. It doesn't have to be repeated, which can make it very, very problematic. And the reason it can happen after only a single trial is it's an example of preparedness, which is an interesting phenomenon that's been discovered in more recent classical conditioning research. Preparedness basically refers to the fact that some animals are predisposed to become conditioned to certain stimuli more than other stimuli.

So humans, and some other, many other animals, it seems, are preconditioned, basically by evolution, to associate feeling sick with eating something bad. Obviously, that's the evolutionary advantage of that is to avoid eating things that are decomposing or infected, poisonous, it's much harder to be conditioned to, say, sounds or certain colours, for example. Other animals are much easily, for example, certain, I think it was ducks or maybe it was pigeons, but some type of bird was much more easily conditioned to a taste of water as opposed to something else. So it depends on the organism and the different senses that they use. If a particular sensory modality is more important for a particular organism, it's more

likely that evolution will have prepared them to be strongly conditioned using that modality. Okay, so that's Taster version. Now I just want to talk about some other applications of classical conditioning because I think too often when this is presented in an intro site course or textbook or something, you know, they go through Pavlov's theory in the condition, non-conditioned stimulus and so on, but they don't really explain why this is important or interesting because it sounds kind of dry. But it is actually very relevant because, remember, although classical conditioning requires some kind of inherent innate reflex, these are actually quite common. And so there are many reflexes that humans and other animals exhibit, which can then be conditioned

and can actually change behavior in very important ways. So some examples are drug tolerance where the behavior or environment of drug taking functions as a signal or condition stimulus that predicts the introduction of the drug to the body. So what can actually happen is that the body can start releasing, can trigger an anticipatory response. which would be the conditioned response, such as the secretion of certain chemicals that help to eliminate the drug from the body. So simply being in the environment where someone takes drugs, these could be recreational drugs or medical drugs, or, you know, seeing the needles or whatever, or even something like alcohol, seeing a bottle of beer, can become conditioned with physiological, neurochemical responses that actually change your physiology.

Another example is conditional immune response. is that some experiments have demonstrated that exposure to particular odors can be conditioned when associated with some illicit substance which will trigger an immune response. So after a certain number of trials, the immune response, as measured by a number of a certain type of white blood cells, for example, actually increases in the organism merely after being exposed to a particular odor, even without being exposed to the actual pathogen that would actually trigger the immune response. So basically the immune system itself can respond to, can be classically conditioned. Another very common example is emotional responses.

There are obviously many, you probably know this yourself, situations where very innocuous stimuli, like seeing a certain person or hearing certain words or being in a certain location, can be conditioned so that they elicit very strong emotional reactions like fear, anger, or anxiety, etc. Sexual response is another case of that. So, for example, if someone sees a microphone, sees a stage, a podium, so on, they may have associated that stimuli with public speaking, which they find difficult to do, therefore they begin to feel anxious or even have a panic attack in response to that. And so, as I was saying, sexual anticipation or the sexual response is a complicated emotional neurochemical reaction, which once again is subject to classical conditioning. So one particularly interesting experiment with rats, the male rats were provided with sexual partners, with multiple sexual partners in the same environment for a number of days. And it wasn't long before that all the rats had to do was be placed in that environment, even without any sexual partners, and an eight-fold rise in sexual hormones was measured.

So basically the sexual hormones, the endocrine system of these rats was responding to the conditioned stimulus producing in conditioned response of sexual anticipation. preparatory to copulation. Classical conditioning has also been proposed as an explanation for sexual parapherias, basically sexual fetuses where people have this sort of strange, aroused by rather strange stimuli. It could be that those stimuli were originally paired with some other unconditioned stimulus, which then resulted in them becoming conditioned, although I don't think that that has actually been proven, but it's certainly plausible, given what we know about classical conditioning.

Okay, so that's all I want to say about classical conditioning. It has many applications, as I've just tried to illustrate, Keep a look out for the follow-up to this on Opera Ant Conditioning, which will be peering shortly. Thank you for listening, and I'll talk to you soon.