In the 1990s, a group of researchers at MIT studied mice to learn more about how habits are formed in the brain. The mice had to find their way to a piece of chocolate that'd been placed at the end of a T-shaped maze. Using special equipment, the researchers could monitor the brain activity of the mice as they sniffed their way to the chocolate.
Their brain activity spiked when the mice were first put in the maze. They could smell the chocolate, and they began searching for it. When the researchers repeated the experiment, however, they noticed something interesting.
As the mice gradually learned where the chocolate was and memorized how to get there – go straight, then turn left – their brain activity decreased.
Turning a sequence of actions into an automatic routine is known as "chunking," and it forms the basis of all habit formation. Its evolutionary role is clear and crucial: it allows the brain to efficiently save energy and perform common tasks.
Hence, even a complicated act that demands concentration at first, like finding a piece of chocolate in a maze or backing out of the driveway, eventually becomes an effortless habit. In fact, according to a 2006 paper by a researcher at Duke University, as many as 40 percent of the actions we perform each day are based on habit.
In general, any habit can be broken down into a three-part loop:
First, you sense an external cue – say, your alarm clock ringing. This creates an overall spike in your brain activity as your brain decides which habit is appropriate for the situation.
Next comes the routine, meaning the activity you're used to performing when faced with this particular cue. For example, you march into the bathroom and brush your teeth with your brain virtually on autopilot.
Finally, you get a reward – a feeling of success and, in this case, a minty-fresh tingling sensation in your mouth. Your overall brain activity increases as your brain registers the successful completion of the activity and reinforces the link between the cue and the routine.
Habits are incredibly resilient. In some cases, people with extensive brain damage can still adhere to their old habits. Just consider Eugene, a man with severe brain damage caused by encephalitis. When asked to point at the door leading to the kitchen from his living room, he couldn't do it. But when asked what he would do if he were hungry, he walked straight into the kitchen and took down a jar of nuts from one of the cabinets.
Eugene could do this because learning and maintaining habits happen in the basal ganglia, a small neurological structure embedded deep in the brain. Even if the rest of the brain is damaged, the basal ganglia can function normally.
Unfortunately, this resilience means that, even if you successfully kick a bad habit, like smoking, you will always be at risk of relapsing.
