Iván Pavlov was a Russian physiologist best known for his research on classical conditioning. He conducted experiments with dogs, demonstrating how they could learn to associate a neutral stimulus, like a bell, with food. This led to the dogs salivating at the sound of the bell, even when no food was presented. Pavlov's work laid the foundation for behaviorism in psychology, influencing many later psychologists, including B.F. Skinner and John B. Watson. His findings have had a lasting impact on various fields, including education, therapy, and animal training, highlighting the importance of learned behaviors.