When an animal performs a particular behavior and the consequences of that behavior are in some ways reinforcing to that animal, the animal is likely to repeat that behavior. If any of these consequences is reinforcing to the whale, the whale is likely to repeat the splashing behavior. When an animal responds with a behavior that is close to what the trainer wants, the trainer delivers a positive reinforcer. As a result, the animal increases the frequency, intensity, and duration of that particular behavior. For example, if a dolphin leaps into the air and a reinforcer follows, the behavior of leaping is like to increase in frequency, duration, and intensity under the same conditions.
Humans learn by the same principles.
For example, consider the behavior of putting money into a candy machine. That behavior is reinforced by the candy that follows. We are likely to repeat that behavior. The behavior of putting money into a candy machine is reinforced by the candy that follows. A positive reinforcer is any consequence that increases the frequency of the preceding behavior.