Why are some behaviors so incredibly difficult to change? This is a mystery to all of us--to the general public, to patients, and to professionals including physicians and therapists and educators. And, but I’ll come to this later, it’s a mystery to neuroscientists as well.
I can think of two examples:
Depression and anxiety disorders are not always easy to treat, but once they do respond, whether to therapy, medication or other approaches, it’s not unusual for symptoms to nearly disappear. In stark contrast, symptoms of OCD and anorexia often only partly resolve--even with extensive treatment. And drug abuse can be difficult to keep in remission: even after years of sobriety, full-blown drinking or drug use can be easily induced by environmental cues--the proverbial ‘people, places and things’ that remind former users of their days of active intoxication, and can trigger complex sequences of drug-seeking behaviors.
Why is that?
In the past few years, neuroscientists have come up with a compelling explanation. In brief, that these disorders result at least in part from what is called ‘habit learning.’ Habit learning is incredibly valuable, since it relieves our minds of the burden of consciously working throughout routine daily activities. It protects us: for instance, while driving a car, we rely on habit learning to keep us safe in a constantly-changing environment, and don’t really have to ‘think’ every time we put on the brakes or change lanes. We can even have a conversation or listen to the radio without endangering our lives. Obviously, innumerable habits of this sort and others make our lives possible.
Habit learning theory brings together these and other seemingly unrelated conditions.
According to the habit learning theory, anorexia nervosa, OCD, and drug abuse all involve sequences of thought and behavior that were initially easily controllable. At first, they were based on ‘reward dependent learning’: at the beginning, it felt good for a young woman to diet, for instance. Checking the lock on his front door several times relieved a man’s worries. And having a few drinks made you feel better after a long day of work.
But over time, these behaviors become habitual: they have, in a sense, gone far beyond the immediate benefits that they evoked. Weight loss begins to become a goal in itself. Checking relieves anxiety, but only momentarily, and needs to be repeated many times just to ward away further anxiety. Drinking no longer feels good, but not drinking feels worse. As such habits develop and strengthen, the external world slips away.
Once they are locked into habit circuitry, such behaviors tend to be repeated month after month, year after year, regardless of environmental consequences, and regardless of whether they are still rewarding or not. And, most frustratingly, such habits may continue for months and years, regardless of whether we want to continue those behaviors.
Take eating, for example. Obviously, our society’s obsession with appearance and weight control compels all of us--but particularly young women--to focus on certain behaviors. We all watch our diets these days, we all try to get regular exercise, and no doubt, many of us stand in front of the mirror each morning or night, wishing that what we saw there better matched our society’s ideal body types. And so, we tend to avoid fattening foods, or carbs or gluten or whatever we believe to be unhealthy; we try to go to the gym regularly; and we develop the habit of practicing a level of self-denial for reasons of health or appearance or both.
If we’re lucky, the habits we develop will be ‘good habits’--or at least, not overtly harmful. Our sequences of thoughts and behaviors related to health will become ‘habitualized’ so to speak, past the point of immediate rewards, so we will be able to fend off the cheesecake at a fancy restaurant, and to push ourselves to go jogging even though the weather is gloomy today.
But for some of us, the unlucky ones, our habits will go too far, will escape from us. They will become our masters, despite what we might want.
Reward-dependent learning and habit learning, as neuroscientists have shown, involve different brain circuits. Whereas reward-dependent learning tends to involve the front parts of the brain, the cortex and the temporal lobe and the hippocampus, habit learning tends to involve the lower parts of the brain, including the striatum and basal ganglia.
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