Every morning, millions of people reach for their phones before they are fully awake, brush their teeth in exactly the same order, and take the same route to school or work. None of these actions requires much thought. They are habits — behaviours that have been repeated so often that they now run almost automatically. Understanding how habits work can help us change the ones we do not like.
Researchers often describe a habit as a loop with three parts. First comes a cue, a signal that tells the brain to start the behaviour. The cue might be a time of day, a place, a feeling, or even another person. Next comes the routine, which is the behaviour itself. Finally there is a reward, something pleasant that makes the brain want to repeat the loop next time. For example, the smell of a bakery may lead you to buy a pastry, and the sweet taste makes it more likely that you will stop there again.
Why does the brain bother creating habits? The answer is efficiency. Thinking carefully about every small decision takes a great deal of mental energy. When a behaviour becomes a habit, control of it shifts to deeper parts of the brain, such as a region called the basal ganglia, and the thinking part of the brain is free to concentrate on other things. This is why you can walk home along a familiar street while planning your weekend, but must pay close attention in an unfamiliar neighborhood.
Unfortunately, the brain cannot tell the difference between good and bad habits. The same loop that helps us remember to lock the door also keeps us snacking in front of the television. Breaking a bad habit is difficult because the cue and the craving for the reward remain even when we decide to stop. Many experts therefore suggest that instead of trying to erase a habit, we should keep the cue and the reward but replace the routine. Someone who always eats sweets when bored, for instance, might go for a short walk instead.
Building a new habit takes patience. In one well-known study, volunteers needed anywhere from a few weeks to several months before a new behaviour, such as drinking a glass of water with a meal, felt automatic. The lesson is encouraging: missing a single day did not ruin the process. What mattered most was repeating the behaviour in the same situation, again and again, until the brain took over.