Operant conditioning and classical conditioning are two fundamentally different forms of learning. Classical conditioning, discovered by Ivan Pavlov, is learning through association—a neutral stimulus becomes linked with an automatic, involuntary response. For example, Pavlov's dogs learned to salivate at the sound of a bell because the bell was repeatedly paired with food. In classical conditioning, the learner is passive; the behavior happens automatically and requires no conscious choice, no reward, and no punishment. Operant conditioning, on the other hand, was developed by B.F. Skinner and is learning through consequences—the likelihood of a voluntary behavior is shaped by what happens after it. Here, the learner is active, deliberately performing behaviors and then adjusting them based on outcomes. In operant conditioning, a behavior is strengthened by reinforcement (adding something pleasant or removing something unpleasant) and weakened by punishment (adding something unpleasant or removing something pleasant). For example, a student who studies hard and receives praise is more likely to study again, while a student who breaks curfew and gets grounded is less likely to repeat that behavior. In short, the key difference is this: classical conditioning pairs a stimulus with an automatic response, while operant conditioning pairs a behavior with a consequence.