B.F. Skinner described four quadrants of operant conditioning. Positive reinforcement adds something pleasant (treat after a sit). Negative reinforcement removes something unpleasant (releasing leash pressure when the dog walks nicely). Positive punishment adds something aversive (a leash jerk). Negative punishment removes something pleasant (turning away when a dog jumps). Modern animal training emphasizes positive reinforcement and negative punishment because they build trust and encourage willing cooperation. Aversive methods (positive punishment, negative reinforcement) can suppress behavior in the short term but risk fear, anxiety, aggression, and damaged relationships. Understanding these quadrants helps pet owners evaluate training methods and choose approaches that prioritize the animal's emotional welfare alongside behavioral goals.