Q.A student who once had a panic attack during a Physics exam now feels anxious every time she enters that particular exam hall, even for a different subject. Explain this using the concepts of classical conditioning.

Classical conditioning is a form of learning first investigated by the Russian physiologist Ivan Pavlov, who discovered it while studying digestion rather than learning itself. Pavlov noticed that dogs in his digestion experiments began salivating merely at the sight of an empty food plate, well before any food was actually presented. To study this systematically, he harnessed a hungry dog in a chamber fitted with a tube from the dog's salivary glands to a measuring glass, so that saliva output could be recorded precisely. In the key procedure, a bell was sounded immediately before meat powder was given to the dog, repeated over many trials; eventually, when the bell was sounded alone, without any food following it, the dog still salivated — showing that a new response had been learned purely through association.

This experiment gives classical conditioning its core vocabulary. Food is the Unconditioned Stimulus (US) because it triggers salivation reflexively, without any learning; the salivation it produces is the Unconditioned Response (UR). The bell begins as a neutral stimulus producing no specific response, but after repeated pairing with food it becomes a Conditioned Stimulus (CS), and the salivation it now triggers is a Conditioned Response (CR). Because one stimulus (the bell) comes to signal the impending arrival of another stimulus (the food), this kind of learning is described as stimulus-stimulus (S-S) learning — a stimulus signifies the likely occurrence of another stimulus. …