Chapter 1 in Duhigg’s book is The Habit Loop: How Habits Work. It starts with the case of EP, who in 1993 lost a portion of his brain to viral encephalitis. EP was not able to recall anything recent, but his long-term memory seemed to be unaffected. His wife was told she would need to keep a close eye on him, as he would not remember that he had amnesia and his home would seem unfamiliar. However, researchers found that he would regularly take walks and find his way home without any problems, despite not being able to verbalize how to do so: “…the visitor asked Eugene where he lived. ‘I don’t know, exactly,’ he said. Then he walked up his sidewalk, opened his front door…”
Researchers hypothesized that this ability to form habits had somethign to do with the basal ganglia, and studies on rats seemed to show that the basal ganglia was central to recalling patterns and acting on them. The brain essentially looks for cues at the beginning of a routine task, then when it recognizes a cue it goes on a sort of auto-pilot as the routine takes over, and finally there is a reward once the task is completed successfully. This cue-routine-reward process is what Duhigg calls The Habit Loop.
The reason the habit loop is important is precisely because the brain shuts down during the routine. So once a habit is formed, unless you deliberately fight it, the pattern will unfold automatically.
Research shows that these routines and habits never really go away – even if we replace them with something else for a long period of time. This can be positive, like the way you never forget how to ride a bicycle. But it also highlights the difficulty of breaking bad habits when repeatedly exposed to the same old cues. The key, then, is to be very conscious of the cues and rewards if we want to change routines.