observations also reveal that when these areas are activated, they can result in addictive, uncontrollable behaviors that are toxic to self and others. They suggest that areas of the brain associated with desire can run out of control. But to understand how the brain motivates us to want some things but not others, how it creates the experience of /iking, and how it enables us to want things we like by /earning about the world, we must turn to experiments on nonhuman animals, brain scans of healthy humans, the mechanics of mind-altering drugs, conscious and unconscious influences on our choices, and the sad stories of individuals with uncontrollable urges to eat, drink, snort, shoot up, and gamble. This is the evidence that scientists, especially the American cognitive neuroscientist Kent Berridge, have gathered to explain the three core elements of pleasure: wanting, liking, and learning. Often, but not always, the experiences we want or desire are the experiences we like. Often, but not always, the experiences we like are rewarding and good for our health. Often, but not always, we are aware of the experiences we like, and make rational plans to experience them again. Often, but not always, our rational plans to experience what we like makes us happy. Often, but not always, we find ways to maintain our happiness by using self-control to moderate our exposure to pleasurable experiences. The offen refrain refers to the fact that the systems involved in wanting, liking, and learning work in this way most of the time. The but not always refrain is a tip off to exceptions that speak to interesting aspects of the machinery. For example, though we most often want things we like, we can want things we don’t like and like things we don’t want. I want to lift weights, do push-ups and sit-ups to stay fit, but I don’t really like doing any of these exercises. I like the Porsche Boxster sportscar, but don’t want one because it is a gas guzzling environmental nightmare and inc