Classical conditioning: discrimination, phobias and evaluation

Pavlov's procedure

Pavlov studied salivation in dogs. Food (UCS) produced salivation (UCR) without learning. A neutral stimulus (NS), such as a sound, was presented just before the food on many trials. Eventually the sound alone (now the CS) produced salivation (the CR).

Timing matters: the NS needs to come just before, or with, the UCS, and the pairing usually needs repeating.

Generalisation and discrimination

• Stimulus generalisation: stimuli similar to the CS also produce the CR (a dog conditioned to one tone salivates to similar tones). Little Albert's fear spread to a rabbit, a dog and a fur coat.
• Stimulus discrimination: the animal learns to respond only to the CS and not to similar stimuli, because only the CS is followed by the UCS. (The specification prints this term as 'distribution'.)
• Extinction: the CR fades if the CS is presented repeatedly without the UCS.
• Spontaneous recovery: after extinction and a rest, the CR suddenly reappears, though usually weaker.

Applying it: how a phobia could be learned

A child is bitten by a dog.

• UCS: the bite (pain). UCR: fear.
• NS: the dog. After pairing, the dog becomes the CS and fear is the CR.
• Generalisation: the child becomes afraid of all dogs.

This account leads to treatment by systematic desensitisation, which conditions a new response (relaxation) to the feared stimulus.

Evaluation

• Strength: scientific, controlled laboratory evidence (Pavlov; Watson and Rayner) that is objective and replicable.
• Strength: practical applications, such as systematic desensitisation for phobias.
• Weakness: much evidence comes from animals, and humans may differ (thinking, expectations), so generalisation is limited.
• Weakness: it is reductionist and deterministic, ignoring cognition; not everyone who has a frightening experience develops a phobia.
• Weakness: ethical issues, such as Watson and Rayner conditioning fear in an infant.

Worked example

A cat runs to the kitchen when it hears a tin opener, but not when it hears other kitchen sounds. Name the process and explain it.

1. The tin opener (CS) has been paired with food (UCS); other sounds have not.
2. The cat responds only to the CS.
3. This is stimulus discrimination.

Answer: Stimulus discrimination: the cat responds only to the sound that has been paired with food.

Check yourself

1. A dog salivates to a 500 Hz tone, which is followed by food, but not to a 1000 Hz tone, which never is. This is
   • stimulus discrimination
   • stimulus generalisation
   • spontaneous recovery
   • negative reinforcement
   Show answer

   stimulus discrimination. It responds only to the stimulus paired with food.

2. A conditioned response that has been extinguished reappears after a rest. This is
   • extinction
   • generalisation
   • spontaneous recovery
   • discrimination
   Show answer

   spontaneous recovery. The CR comes back without new pairings.

3. A child is stung by a wasp and becomes afraid of wasps. What is the UCS?
   • The sting
   • The wasp
   • The fear
   • The garden
   Show answer

   The sting. The sting causes pain and fear without learning.

4. In the same example, what is the CS after conditioning?
   • The sting
   • The pain
   • The fear
   • The wasp
   Show answer

   The wasp. The wasp was neutral but now triggers fear.

5. Which is a weakness of classical conditioning as an explanation of phobias?
   • It cannot be tested in a laboratory
   • Not everyone who has a frightening experience develops a phobia
   • It has no practical applications
   • It only uses qualitative data
   Show answer

   Not everyone who has a frightening experience develops a phobia. Cognitive and biological factors also seem to matter.

6. Using classical conditioning, explain how someone could develop a fear of flying after a frightening flight.
   Show answer

   During a flight with severe turbulence (UCS), the person felt fear (UCR). The plane (NS) was paired with the turbulence, so it became a conditioned stimulus that now produces fear (CR) on its own, and this may generalise to airports.. UCS, pairing, then CS and CR.

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Sources

• Pearson Edexcel International Advanced Subsidiary/Advanced Level in Psychology specification, Issue 5 (February 2021)
• Pearson IAL Psychology component guide: WPS02 (Issue 2, November 2024)
• Watson and Rayner (1920), Conditioned emotional reactions (Classics in the History of Psychology)

Last updated 8 November 2026. Spotted a mistake? Tell us.