Classical conditioning: how Pavlov’s dogs learned

What is classical conditioning?

• Learning by association: a neutral stimulus becomes linked to one that already triggers a response.
• Discovered by Ivan Pavlov (1890s) while studying digestion in dogs.

The four key terms

• Unconditioned stimulus (US): food. Triggers a response with no learning.
• Unconditioned response (UR): salivating at the food.
• Conditioned stimulus (CS): the bell, once it has been paired with food.
• Conditioned response (CR): salivating at the bell alone.

Acquisition vs. extinction

• Acquisition: CS and US paired repeatedly; works best when the CS comes about half a second before the US.
• Extinction: CS shown without the US until the CR fades.
• Spontaneous recovery: after a rest, the extinguished CR briefly returns. The learning was suppressed, not erased.

Generalization & discrimination

• Generalization: responding to stimuli similar to the CS (a slightly different bell).
• Discrimination: learning to respond only to the exact CS.

Real-world example (on the exam)

• Little Albert (Watson & Rayner, 1920): a loud noise (US) paired with a white rat (CS) produced fear (CR) that generalized to other furry objects.
• Professor flagged this one: “know how to label every part of this study.”