The document discusses classical conditioning, which was discovered by Ivan Pavlov in his experiments with dogs. Pavlov found that dogs would salivate not just when food was present, but also when they heard a sound that preceded the food, like a metronome. Over time, the sound alone came to trigger salivation, demonstrating that a neutral stimulus can become associated with an unconditioned response through repeated pairings. This is known as classical conditioning. The document outlines Pavlov's experiments and findings in detail, and discusses key concepts and terminology in classical conditioning like conditioned stimulus, conditioned response, unconditioned stimulus, and unconditioned response. It also examines complications that can arise in conditioning like overshadowing and blocking.