Basic Psychology, Cognitive Psychology, Learning and Memory

Classical Conditioning

Classical conditioning is a type of learning that had a major influence on the school of thought in psychology known as behaviorism. Discovered by Russian physiologist Ivan Pavlov, classical conditioning is a learning process that occurs through associations between an environmental stimulus and a naturally occurring stimulus.The discovery was not intentional. He came across it by accident while conducting experiments on digestion in the early 1900s. Pavlov then decided to devote his entire life. Pavlov first discovered classical conditioning serendipity when he was experimenting on his dog ‘Circa’ in 1905. He also went on to win the Nobel Prize in science for his discovery.

The Development of Classical Conditioning Theory

Phase 1: Before Conditioning

At first he thought that there is no need to teach some responses to dogs (like salivating when the food is near), and that these responses are hard-wired to dog’s brain. He termed these as Unconditioned Responses(UCR).During this phase of the processes, the unconditioned stimulus (UCS) results in an unconditioned response (UCR). For example, presenting food (the UCS) naturally and automatically triggers a salivation response (the UCR).

pavlovdog.jpg

Phase 2: During Conditioning

Then one day he observed that these dogs also start salivating when a bell was ranged and food was served everyday. This made him realize that these dogs have learnt to associate the food with the bell and this has triggered the same response (salivation) as before. During the second phase of the classical conditioning process, the previously neutral stimulus is repeatedly paired with the unconditioned stimulus. As a result of this pairing, an association between the previously neutral stimulus and the UCS is formed. At this point, the once neutral stimulus becomes known as the conditioned stimulus (CS). The subject has now been conditioned to respond to this stimulus.

Phase 3: After Conditioning

Once the association has been made between the UCS and the CS, presenting the conditioned stimulus alone will come to evoke a response even without the unconditioned stimulus. The resulting response is known as the conditioned response (CR).

classical conditioning diagram


  • UnConditioned Stimulus(UCS) is one that unconditionally, naturally, and automatically triggers a response. For example, when you smell one of your favorite foods, you may immediately feel very hungry.

  • UnConditioned Response(UCR) is the unlearned response that occurs naturally in response to the unconditioned stimulus.

  • Conditioned Stimulus(CS) is previously neutral stimulus that, after becoming associated with the unconditioned stimulus, eventually comes to trigger a conditioned response.

  • Conditioned Response(CR) is the learned response to the previously neutral stimulus.

classical conditioning

Key Principles of Classical Conditioning

Behaviorists have described a number of different phenomena associated with classical conditioning.

1. Acquisition

Acquisition is the initial stage of learning when a response is first established and gradually strengthened. During the acquisition phase of classical conditioning, a neutral stimulus is repeatedly paired with an unconditioned stimulus. After an association is made, the subject will begin to emit a behavior in response to the previously neutral stimulus, which is now known as a conditioned stimulus. It is at this point that we can say that the response has been acquired.

2. Extinction

Extinction is when the occurrences of a conditioned response decreases or disappears. In classical conditioning, this happens when a conditioned stimulus is no longer paired with an unconditioned stimulus.

3. Spontaneous Recovery

Sometimes a learned response can suddenly reemerge even after a period of extinction. Spontaneous Recovery is the reappearance of the conditioned response after a rest period or period of lessened response. If the conditioned stimulus and unconditioned stimulus are no longer associated, extinction will occur very rapidly after a spontaneous recovery.

4. Stimulus Generalization

Stimulus Generalization is the tendency for the conditioned stimulus to evoke similar responses after the response has been conditioned.

In John B. Watson’s famous Little Albert Experiment, for example, a small child was conditioned to fear a white rat. The child demonstrated stimulus generalization by also exhibiting fear in response to other fuzzy white objects including stuffed toys and Watson own hair.

5. Stimulus Discrimination

Discrimination is the ability to differentiate between a conditioned stimulus and other stimuli that have not been paired with an unconditioned stimulus.

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