Classical conditioning: when a signal starts to matter

Transcript

RyanPicture a woman named Dana. Her cancer treatment ended two years ago, and it worked. Today she's walking into the same clinic for a routine checkup. No medicine today, nothing in her system. And before she even reaches the front desk, her stomach turns.

SoheeNothing in that building can make her sick anymore. And yet her body reacts as if it can.

RyanWelcome to EPPP Prep, the podcast. I'm Ryan.

SoheeAnd I'm Sohee. Today it's classical conditioning. It's one of the oldest ideas in the learning chapter, and it still explains a lot of what clinicians see, from that clinic nausea to fears, and to how we treat them.

RyanLet's start with what learning is. The OpenStax psychology textbook defines it as a relatively permanent change in behavior or knowledge that results from experience.

SoheeWhich sets it apart from reflexes and instincts. Those are innate, unlearned behaviors we're born with. Every healthy baby has a sucking reflex at birth. Nobody teaches it.

RyanAnd classical conditioning, also called Pavlovian conditioning, is how organisms learn to associate stimuli that repeatedly happen together.

SoheePavlov's story is a good one, because he wasn't studying learning at all. He was a physiologist, not a psychologist. His interest was the digestive system, and he measured how much saliva dogs produced in response to food.

RyanAnd the dogs started salivating early. At the sight of food, at an empty food bowl, even at the sound of the lab assistants' footsteps. Pavlov called these psychic secretions.

SoheeLet's lay out the vocabulary, because questions here are precise. Meat powder was the unconditioned stimulus, a stimulus that elicits a reflexive response. Salivating to it was the unconditioned response, a natural, unlearned reaction.

RyanThen there's a neutral stimulus, a tone, which doesn't naturally elicit a response. Pavlov sounded the tone and then gave the meat powder, over and over.

SoheeEventually the tone alone brought salivation. Now the tone is the conditioned stimulus, and salivating to the tone is the conditioned response.

RyanA way to keep them straight. Pavlov described unconditioned, meaning unlearned, responses, and conditioned, meaning learned ones. The response can even look the same, salivation both times. What changes is what sets it off, and whether that took learning.

SoheeOrder matters too. The neutral stimulus comes immediately before the unconditioned stimulus. And typically there should be only a brief interval between them.

RyanBack to Dana. Let's map it. The chemotherapy drugs are the unconditioned stimulus. Getting sick from them is the unconditioned response. The clinic is the conditioned stimulus, and the nausea she feels there now is the conditioned response.

SoheeOpenStax uses nearly this exact case, a patient named Moisha. And it adds a twist. She always saw a syringe before the drugs, so she comes to respond to syringes with nausea too.

RyanThat's higher-order, or second-order, conditioning. The office, already a conditioned stimulus, serves to condition another stimulus, the syringe. And the textbook notes it's hard to achieve anything above second-order conditioning.

SoheeNow the processes. Acquisition is the initial period of learning, when the organism connects the neutral stimulus with the unconditioned stimulus.

RyanExtinction is the decrease in the conditioned response when the unconditioned stimulus is no longer presented with the conditioned stimulus. Pavlov sounded the tone with no meat powder, and soon the dogs stopped responding.

SoheeBut extinction isn't erasure. After a couple of hours of rest, the dogs salivated to the bell again. Pavlov called that spontaneous recovery: the return of a previously extinguished conditioned response after a rest period.

RyanSo if a response that was extinguished shows up again after a pause, the word you want is spontaneous recovery, not reacquisition.

SoheeThen the pair that people swap most. Stimulus generalization is showing the conditioned response to stimuli similar to the conditioned stimulus. Stimulus discrimination is learning to respond differently to similar stimuli, so the response comes only to the conditioned stimulus.

RyanMoisha shows both. She learned not to feel ill at doctors' visits for other reasons, like her annual physical. That's discrimination. But she still felt ill visiting other oncologists, or other doctors in the same building. That's generalization.

SoheeAnd there's a gradient. The more similar a stimulus is to the conditioned stimulus, the more likely the conditioned response.

RyanPause and think. A child is stung by a bee in the garden. Afterward she startles at the buzzing of flies, too. What explains the fear of the flies' buzzing?

SoheeStimulus generalization. The buzzing became a conditioned stimulus for fear, and a similar sound, a fly's buzz, now triggers the same response.

RyanNow an exception to that brief-interval rule. Taste aversion. Here several hours can pass between eating something and getting sick, and the learning can happen from a single instance.

SoheeGarcia and Koelling showed in 1966 that taste aversions could be conditioned, and also that there were biological constraints on learning. Rats with flavor and illness pairings all learned to avoid the flavor. None of the rats with lights and sounds paired with illness learned to avoid the lights or sounds.

RyanThe textbook's explanation is evolutionary. This may be an adaptation that helps organisms quickly learn to avoid harmful foods.

SoheeAnd one more modern piece. Robert Rescorla showed how powerfully an organism learns to predict the unconditioned stimulus from the conditioned stimulus. With Allan Wagner he developed a formula for the probability that an association is learned, given how well the conditioned stimulus predicts the unconditioned one. That's the Rescorla-Wagner model.

RyanThe textbook's example is dinner. Ari's dad always serves dinner at six, so six o'clock reliably predicts dinner, and Ari gets hungry right before six. Soraya's family eats at five, six or seven, so she's less likely to link six o'clock with dinner.

SoheeSo it isn't only how often two things occur together. It's how reliably one predicts the other.

RyanNow to humans and emotion. John B. Watson is considered the founder of behaviorism. He held that psychology must focus on outward, observable behavior that can be measured.

SoheeAnd he believed Pavlov's principles could be extended to conditioning human emotions. In 1920, at Johns Hopkins, Watson and his graduate student Rosalie Rayner studied a baby nicknamed Little Albert.

RyanAlbert enjoyed playing with a white rat. Then, each time he touched the rat, Watson struck a hammer against a metal bar behind his head. The noise frightened him, and after repeated pairings the rat alone frightened him.

SoheeQuick labels. The loud noise is the unconditioned stimulus. Fear of the noise, the unconditioned response. The white rat, the conditioned stimulus. Fear of the rat, the conditioned response.

RyanAnd days later Albert was afraid of other furry things too: a rabbit, a furry coat, even a Santa Claus mask. Generalization again.

SoheeTwo cautions from the textbook. There's no evidence Albert experienced phobias in later years. And the study would be considered unethical by today's standards.

RyanHere's the hopeful half of the story. If fear can be learned, can it be unlearned? Exposure therapy was first reported in 1924 by Mary Cover Jones, who is considered the mother of behavior therapy.

SoheeShe worked with a boy named Peter who was afraid of rabbits. She placed a caged rabbit across the room while he ate his afternoon snack, and over several days moved it closer. After two months, Peter could hold and pet the rabbit while eating.

RyanHer goal was to replace fear with relaxation, a response that's incompatible with fear. That's counterconditioning: the client learns a new response to a stimulus that used to elicit an undesirable one.

SoheeThirty years later, Joseph Wolpe refined Jones's techniques into systematic desensitization. The person builds a hierarchy from the least anxiety-producing stimulus up to the feared object, and pairs each step with relaxation techniques taught beforehand.

RyanThe reasoning, in the textbook's words: a person cannot be nervous and relaxed at the same time.

SoheeAversive conditioning runs the other way. It uses an unpleasant stimulus to stop an undesirable behavior. With Antabuse, drinking alcohol brings side effects like nausea and vomiting, and with repeated pairing the client associates alcohol with unpleasant feelings.

RyanSo how might the exam test this? Mostly by asking you to label. Which is the conditioned stimulus? Extinction or spontaneous recovery? Generalization or discrimination?

SoheeAnd the tempting wrong answers swap the pairs. A quick check: did this stimulus need learning to have its effect? If not, it's unconditioned.

RyanAnother trap is mixing classical with operant conditioning. In classical conditioning, something in the environment triggers a reflex automatically. In operant conditioning, the organism learns to associate a behavior with its consequence.

SoheeSo if the key event comes first and triggers a reflex or an emotion, think classical. If a consequence follows a behavior and changes how often it happens, think operant. That's our next episode.

RyanPause and think, one more. A man afraid of elevators first learns to relax. Then, step by step, starting with the least frightening, he works up a ladder of elevator situations while staying relaxed. What's the technique, and who refined it?

SoheeSystematic desensitization, from Joseph Wolpe, building on Mary Cover Jones. A graded hierarchy paired with relaxation.

RyanLet's recap. Classical conditioning pairs a neutral stimulus with an unconditioned stimulus until the neutral one, now a conditioned stimulus, brings a conditioned response by itself.

SoheeAcquisition builds the link. Extinction weakens the response when the unconditioned stimulus stops coming. Spontaneous recovery brings it back after rest.

RyanGeneralization spreads the response to similar stimuli. Discrimination narrows it. Higher-order conditioning links a new stimulus to an old conditioned one.

SoheeTaste aversion can form over hours and in one trial, and Garcia and Koelling showed biology limits what's learned. Rescorla and Wagner showed that prediction matters.

RyanAnd Watson showed fear can be conditioned, while Jones and Wolpe showed it can be counterconditioned.

SoheeIf these four labels have ever blurred together for you, please know that's very common. Map them onto one example of your own, like Dana's clinic, and they start to stick.

RyanThanks for learning with us. Try a few practice questions while it's fresh, and we'll see you next time on EPPP Prep.

Loading the read-along timings…