[music playing]

[thunder]

Narrator: A rumble.

[rain falling]

Narrator: A summer shower.

[beeping]

Narrator: A beep. A cooked meal.

[music playing]

Narrator: A melody. A reinforcement. We have learned that these things somehow go together. Another example.

Robert Epstein: I got a speeding ticket not too long ago. And I noticed that, for a while after that, I was feeling very nervous whenever I saw a police officer or a police car. I was getting, like, this kind of racy feeling, you know. Why?

Well, because a stimulus which, in and of itself, isn't very stimulating— that is, a police car— had been paired recently with something that was very stimulating— namely, a huge fine. When you pair a stimulus that's not very important and doesn't produce much of a reaction with another stimulus that produces a huge reaction, there's a spread of effect from the important stimulus to the unimportant stimulus. That is classical conditioning. It's the simplest type of learning there is.

Narrator: The story of classical conditioning begins with the classic experiments of Russian physiologist Ivan Pavlov.

Robert Epstein: In the early 1900s, he was awarded the Nobel Prize for research he had done on how the digestive system works in dogs.

Narrator: Pavlov stumbled into his groundbreaking findings quite by accident. He was studying the salivary responsive of dogs to different types of foods.

Robert Epstein: So he's got the dog basically in restraints. He's got a cannula. It's connected to the salivary glands. Pavlov would put some food— or it was actually a food powder in a dog's mouth. He'd collect saliva from the dog. He noticed that something was happening with these dogs. When the lab assistant would come into the room, the dog would start salivating before the meat ever made it to the dog's mouth.

Narrator: They were demonstrating very powerful principles of learned behavior, and soon Pavlov realized he had come across a very important finding. "Conditioning" is the process of learning associations. The dogs have learned to associate two stimuli— the sound of footsteps and food— and their automatic response was to salivate.

Pavlov's experiments demonstrate the four basic elements of classical conditioning, which he identified. First, you have your unconditioned stimulus. In this situation, the unconditioned stimulus is the plate of food. This is a stimulus that will reliably produce a naturally-occurring reaction in the organism. Next, you have the unconditioned response— the salvation of the dog. This is a reaction that is reliably produced by the presentation of the unconditioned stimulus, the food.

Pavlov called these "unconditioned" stimuli and responses because they occur naturally. Food is a natural biological stimulus, and salivation is an automatic reflex response. They are unlearned or "unconditioned."

Daniel Cervone: If Pavlov replaced the sound of footsteps in the hallway with something systematic, like the ringing of a bell.

[bell rings]

Daniel Cervone: And so has has a paradigm in which a bell was rung. Food is presented. After a few trials like this, the dog salivates when the bell is rung.

[bell rings]

Daniel Cervone: The bell converts from a neutral stimulus to one that, through conditioning, triggers the response of salivation.

[bell rings]

Robert Epstein: Classical conditioning can occur at different levels. For example, if I start with some powerful, biologically important stimulus— like food— pair a neutral stimulus with that— such as a bell— remember, there's a spread of effect from the important stimulus to the neutral stimulus. So now, my neutral stimulus is no longer neutral. The question is— can I now pair the bell with a neutral stimulus and see that spread of effect occur again? That's called "second-order conditioning." Yeah. You can.

Once I have this new reflex, this conditional reflex, that means I have a new stimulus that produces its own response. What happens if I repeat the presentation of that stimulus over and over and over again without pairing it with the biologically important stimulus, with the unconditional stimulus? And the answer is it becomes less and less and less effective.

Narrator: This illustrates extinction— which is the decline of the conditioned response. Even after a conditioned response was extinguished, Pavlov noticed something interesting. If he allowed the dogs to have a brief rest period after extinction and then presented them again with the conditioned stimulus, they displayed a spontaneous recovery of their conditioned response. The bell triggered salivation, just as before.

Robert Epstein: So take this to a practical level. This is exactly what John B. Watson and his student Rosalie Rayner did in a study they published in the 1920s.

[music playing]

Narrator: Pavlov's studies excited behaviorists like John B. Watson. Like Pavlov, Watson believed that psychology should focus on the objective, scientific study of observable behaviors, rather than the subjective interpretations of feelings, memories, or emotions.

So Watson initiated a controversial series of experiments involving a nine-month-old boy dubbed "Little Albert." Watson presented Little Albert with a variety of stimuli— a white rat, a dog, a rabbit, various masks, and a burning newspaper. Albert's reaction, in most cases, was curious indifference

Robert Epstein: What would they do is to pair the presentation of the animal.

Daniel Cervone: So you present this fairly neutral stimulus. Behind the toddler, on the wall, is this big iron bar.

Robert Epstein: Just as he reaches out for the animal, the steel bar is struck.

Daniel Cervone: Which produces a very strong reaction of fear.

Narrator: After several repetitions, Albert began to show what's called "stimulus generalization."

Robert Epstein: He's afraid of others stuff— other small animals, a white furry coat. And famously, for psychology, a Santa Clause mask.

Narrator: Watson believed that the basic laws of learning were the same for all organisms— from rats to dogs to humans— and that almost all human behavior was a result of conditioning. He argued that the goal of psychology was to predict and control behavior through scientific study.

Robert Epstein: And he was, in a sense, rebellious. He already had envisioned that there might be a psychology that looked different than the psychology that existed. So in some ways, this tradition was one of psychology's super success stories. In other ways, what happened is that the early behaviorists— clearly, especially Watson— kind of underestimated the complexity of the human condition. And now, we know a bazillion things that just aren't what Watson was thinking back then.

Narrator: One of the areas glossed over by behaviorists is evolution. That an organism is biologically prepared to learn certain associations is another piece of the puzzle. What shapes this predisposition to react to specific stimuli over millions of years of evolution?

[music playing]

Narrator: If we look around, we see that our lives are full of classically conditioned responses.

[phone vibrating]

Narrator: And most of them have deep cognitive roots in values and expectations passed down over milleniums.

[phone ringing]

Man: April, is it you?

[beeping]

[knocking]

Pizzaman: Delivery?

Man: No. Wrong apartment.

[music playing]