MCAT Content / Associative Learning / Classical Conditioning

Classical Conditioning

Topic: Associative Learning

Classical conditioning, a type of associative learning, occurs when an appropriate response to a stimulus becomes conditioned to respond to another associated stimulus.

Classical conditioning is a form of learning whereby a conditioned stimulus (CS) becomes associated with an unrelated unconditioned stimulus (US) to produce a behavioral response known as a conditioned response (CR). The conditioned response is the learned response to the previously neutral stimulus. The unconditioned stimulus is usually a biologically significant stimulus such as food or pain that elicits an unconditioned response (UR) from the start. The conditioned stimulus is typically neutral and produces no particular response at first, but after conditioning, it elicits the conditioned response.

The best-known of Pavlov’s experiments involved the study of the salivation of dogs. Pavlov was originally studying the saliva of dogs as it related to digestion, but as he conducted his research, he noticed that the dogs would begin to salivate every time he entered the room—even if he had no food. The dogs were associating his entrance into the room with being fed. This led Pavlov to design a series of experiments in which he used various sound objects, such as a buzzer, to condition the salivation response in dogs.

He started by sounding a buzzer each time food was given to the dogs and found that the dogs would begin salivating immediately after hearing the buzzer—even before seeing the food. After a period of time, Pavlov began sounding the buzzer without giving any food at all and found that the dogs continued to salivate at the sound of the buzzer even in the absence of food. They had learned to associate the sound of the buzzer with being fed.

If we look at Pavlov’s experiment, we can identify the four factors of classical conditioning at work:

– The unconditioned response was the dogs’ natural salivation in response to seeing or smelling their food.
– The unconditioned stimulus was the sight or smell of the food itself.
– The conditioned stimulus was the ringing of the bell, which previously had no association with food.
– The conditioned response, therefore, was the salivation of the dogs in response to the ringing of the bell, even when no food was present.

Pavlov had successfully associated an unconditioned response (natural salivation in response to food) with a conditioned stimulus (a buzzer), eventually creating a conditioned response (salivation in response to a buzzer). With these results, Pavlov established his theory of classical conditioning.

In classical conditioning, the initial period of learning is known as acquisition, when an organism learns to connect a neutral stimulus and an unconditioned stimulus. During acquisition, the neutral stimulus begins to elicit the conditioned response, and eventually, the neutral stimulus becomes a conditioned stimulus capable of eliciting the conditioned response by itself. Timing is important for conditioning to occur. Once we have established the connection between the unconditioned stimulus and the conditioned stimulus, how do we break that connection and get the dog, cat, or child to stop responding? In classical conditioning terms, you would be giving the conditioned stimulus, but not the unconditioned stimulus. Pavlov explored this scenario in his experiments with dogs: sounding the tone without giving the dogs the meat powder. Soon the dogs stopped responding to the tone. Extinction is the decrease in the conditioned response when the unconditioned stimulus is no longer presented with the conditioned stimulus. When presented with the conditioned stimulus alone, the dog, cat, or other organism would show a weaker and weaker response, and finally, no response. In classical conditioning terms, there is a gradual weakening and disappearance of the conditioned response.

What happens when learning is not used for a while—when what was learned lies dormant? As we just discussed, Pavlov found that when he repeatedly presented the bell (conditioned stimulus) without the meat powder (unconditioned stimulus), extinction occurred; the dogs stopped salivating to the bell. However, after a couple of hours of resting from this extinction training, the dogs again began to salivate when Pavlov rang the bell. The behavior of Pavlov’s dogs illustrates a concept Pavlov called spontaneous recovery: the return of a previously extinguished conditioned response following a rest period.

This is the curve of acquisition, extinction, and spontaneous recovery. The rising curve shows the conditioned response quickly getting stronger through the repeated pairing of the conditioned stimulus and the unconditioned stimulus (acquisition). Then the curve decreases, which shows how the conditioned response weakens when only the conditioned stimulus is presented (extinction). After a break or pause from conditioning, the conditioned response reappears (spontaneous recovery).

Acquisition and extinction involve the strengthening and weakening, respectively, of a learned association. Two other learning processes—stimulus discrimination and stimulus generalization—are involved in distinguishing, which stimuli will trigger the learned association. Animals (including humans) need to distinguish between stimuli—for example, between sounds that predict a threatening event and sounds that do not—so that they can respond appropriately (such as running away if the sound is threatening). When an organism learns to respond differently to various stimuli that are similar, it is called stimulus discrimination. In classical conditioning terms, the organism demonstrates the conditioned response only to the conditioned stimulus. Pavlov’s dogs discriminated between the basic tone that sounded before they were fed and other tones (e.g., the doorbell) because the other sounds did not predict the arrival of food.

On the other hand, when an organism demonstrates the conditioned response to stimuli that are similar to the conditioned stimulus, it is called stimulus generalization, the opposite of stimulus discrimination. The more similar a stimulus is to the conditioned stimulus, the more likely the organism is to give the conditioned response.


Practice Questions

Khan Academy

Exploring clinical applications of classical conditioning

Tickle me Nim. Do primates speak language?

Cats and dogs and conditioning

MCAT Official Prep (AAMC)

Online Flashcards Psychology Question 18

Sample Test P/S Section Passage 5 Question 30

Sample Test P/S Section Passage 5 Question 31

Practice Exam 1 P/S Section Passage 2 Question 9

Practice Exam 2 P/S Section Passage 9 Question 48

Practice Exam 2 P/S Section Passage 9 Question 49

Practice Exam 4 P/S Section Passage 6 Question 32


Key Points

• Ivan Pavlov is known for his famous experiment with conditioning the salivation response in dogs, which brought about classical conditioning.

• Classical conditioning is a form of learning whereby a conditioned stimulus becomes associated with an unrelated unconditioned stimulus, in order to produce a behavioral response known as a conditioned response.

• By teaching dogs to associate the sound of a buzzer with being fed, Pavlov established the principles of classical conditioning.

• Various behavior therapies for managing fear and anxiety, such as desensitization and flooding, have been developed from Pavlov’s work.

• In classical conditioning, the initial period of learning is known as acquisition, when an organism learns to connect a neutral stimulus and an unconditioned stimulus.

• Extinction is the decrease in the conditioned response when the unconditioned stimulus is no longer presented with the conditioned stimulus.

• When an organism learns to respond differently to various stimuli that are similar, it is called stimulus discrimination.

• When an organism demonstrates the conditioned response to stimuli that are similar to the condition stimulus, it is called stimulus generalization.


Key Terms

condition: To shape the behavior of an individual or animal.

acquisition: period of initial learning in classical conditioning in which a human or an animal begins to connect a neutral stimulus and an unconditioned stimulus so that the neutral stimulus will begin to elicit the conditioned response

classical conditioning: learning in which the stimulus or experience occurs before the behavior and then gets paired or associated with the behavior

conditioned response (CR):  response caused by the conditioned stimulus

conditioned stimulus (CS):  stimulus that elicits a response due to its being paired with an unconditioned stimulus

extinction  decrease in the conditioned response when the unconditioned stimulus is no longer paired with the conditioned stimulus

neutral stimulus (NS)  stimulus that does not initially elicit a response

spontaneous recovery  return of a previously extinguished conditioned response

stimulus discrimination  ability to respond differently to similar stimuli

stimulus generalization  demonstrating the conditioned response to stimuli that are similar to the conditioned stimulus

unconditioned response (UCR)  natural (unlearned) behavior to a given stimulus

unconditioned stimulus (UCS)  stimulus that elicits a reflexive response



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