The professor is talking about stating laws in the science of psychology. Psychology is a relatively new science. Like other sciences, psychology must be able to state laws. A law is a way of organizing knowledge about something so that we can make predictions. When enough knowledge is gained about a subject, a scientist can state precisely what will happen under certain conditions. We experimental psychologists are interested in developing laws about human behavior, so well be able to understand and predict what people do and why they do it. Of course, to develop laws about human behavior, we must assume there's some regularity to it. We can't be psychologists without making assumption. The behaviour follows certain patterns. One of the major law psychology start escaping is called the law of effect. The law of effect states that whether or not a person will repeat a behavior depends on the effect that behavior has. If an action is rewarded, it's likely to be repeated. If the action is not rewarded, or if it's punished, IT's not likely to be repeated. How do psychologists state laws? First, using available knowledge, a psychologist makes a hypothesis about behavior. Then the psychologist tests the hypothesis through an experiment. But even if the experiment proves the hypothesis was correct, it's not yet a law. it's just the beginning of the work to arrive at a law that will apply to all humans. Many repetitions of the experiment must be conducted under different conditions. Only repeated verification, especially proof that the behavior can be predicted, will result in a law.