Maybe you chew your fingernails when you're nervous. Or scarf down chocolate when you're sad. Or take home a stray kitty whenever you see one, until the SPCA has to come rescue them all and have you arrested for being a hoarder.
Chances are, you have a few habits you wish you didn't have, and quite possibly you've tried (and tried and tried) to break them. Scientists are learning why you may have failed (and failed and failed). In fact, they now know that once you have a habit, you can never really unlearn it.
"Once it's there, it's there," says Ann Graybiel, the Walter A. Rosenblith professor of neuroscience at the Massachusetts Institute of Technology in Cambridge, Mass. "It really will never leave."
Still, no need to panic.
The fact is, even though you can never simply delete habits from your brain and be rid of them once and for all, you can stop indulging in them if you really, really want to -- and scientists have been learning more about that, as well. But be warned: Breaking up with a habit is ha-a-a-rd to do.
"There's an expenditure of energy involved in changing behavior," says Dr. Nora Volkow, director of the National Institute on Drug Abuse in Bethesda, Md. "That's where motivation comes in."
Habits are learned behaviors -- ones you've become trained to do almost without thinking. When you're first learning to drive a stick-shift car, it may seem beyond the power of any mortal to coordinate such complex maneuvers: pushing in the clutch, shifting gears, letting out the clutch, stepping on the gas. You stall at lights. You roll backward down a hill or two. But you start to get the hang of it, and before you know it, you're shifting automatically (so to speak).
Shifting has become a habit -- something you've done so often that you hardly have to think about it any more.
"In habit learning, neural patterns get drilled into the brain," Graybiel says. "This is good for survival."
And, for the most part, it's good for simply getting through the day. All the little routine things you do by habit -- from putting on your shoes to combing your hair to picking up after your dog -- leave your mind free to think and plan and solve problems and contemplate the important issues of our time, like, say, how did computer geek Steve Wozniak ever survive so long on "Dancing With the Stars"?
Goal in sight
But then there are those other habits, the kind that can throw big monkey wrenches into your life -- overeating, over-shopping, biting your nails, not biting your tongue, biting off more than you can chew and then procrastinating.
Habits you'd like to disown.
Scientists theorize that in acquiring a habit, be it good, bad or innocuous, you typically start out with "goal-directed behavior," meaning you perform a certain action in a certain situation because you expect to reach a certain goal. But if you repeat this same action in this same situation over and over, you get to the point where you take a particular action in a particular situation simply because you're in that situation. Your goal has dropped out of the equation.
There's evidence to back up this theory. In one Duke University study, currently under review for publication, researchers gave students popcorn to eat while watching movie trailers. Sometimes the popcorn was fresh, popped an hour before the movies started. Sometimes it was stale, popped seven days before.
All the students had a preference for the fresh popcorn. And the researchers found that people who didn't make a habit of eating popcorn at the movies showed goal-directed behavior (the goal was eating something tasty): They ate much more popcorn when it tasted good than when it didn't, "which is what you would probably expect everyone to do," says Wendy Wood, professor of psychology and neuroscience at Duke and a study co-author.
But you would be wrong. People who had a popcorn-movies habit seemed to eat the popcorn simply because they were at the movies: They ate just as much regardless of whether it tasted good or, as Wood termed it, "disgusting."
Human beings are hard to study, so it's lucky for scientists in this field that rats, like people, can be creatures of habit.
In studies, researchers have trained rats to press a lever to get the reward of a food pellet and then started putting food poisoning on the pellet to make the rats feel ill. Some rats then stopped pressing the lever, or at least pressed it much less often. Researchers inferred that these rats had been showing goal-directed behavior -- they'd been pressing the lever to get the food, and, presumably, were feeling shortchanged by the sickening pellet.
But other rats kept pressing the lever as much as ever. Researchers inferred that the sickening pellet didn't faze these rats because pressing the lever had become a hard habit to break.