This is not the first book on habits and the brain that I've read, so a lot of the case studies presented were already familiar to me. The case of Eugene Pauly first came to my attention in Moonwalking with Einstien by Joshua Foer, but being examined under the focus of habits, the case took on a different light. Despite his inability to form new memories Eugene was able to form new habits though physical repetition, what's commonly referred to as "muscle memory". We develop such habits help the brain save energy. When we encountered a predator on our daily forage, it made sense to shut down all functions but the ones that are key for survive, the oft-referenced "fight or flight" responses. It's also how we can turn off the stove, walk out of the kitchen, and immediately forget whether we've turned off the stove. That motion of reaching out and turning the knob is so commonplace, our brains don't register it. Habits can also be to our benefit. Closing up the bookstore, I used to constantly second-guess whether I had locked the doors and often had to go back to check. Then I had to double-check my double-checking. I fixed this by establishing a new habit. Now, when I set the empty cash register trays in front of each door, I reach up with my free hand and push on the door to check it. It's automatic now. This way, I can just glance from the other side of the store. The trays are in place? Then the doors are locked. A lot of the science in The Power of Habit is saying in a new way things that have been said before, but, as with many topics dealing with our behaviour, having a lot of different perspective can be helpful. Duhigg's metaphor for the "power of habit" is the habit loop. Habits are made up of a cue, a routine and a reward. Like Pavlov's dog, we respond to the cue by performing the routine, even when we know the reward isn't very good for us, or when we're trying to abstain. The key to changing habits, according to Duhigg is identifying these three elements; cue, routine, reward; then using that understanding to tweak our behaviour. We know we're going to come up against temptation (what Duhigg calls "inflection points"), so it's best to have a plan, and a plan repeated becomes a habit. Two of Duhiff's examples (of which he has many) struck me as especially interesting: in one study hip- and knee-replacements, patients who wrote down detailed pain management strategies recovered much more quickly than those who made no such plans; at Starbucks, employee training includes in planning how baristas will respond when a customer is yelling at them, or when the line is extending out the door and they feel overwhelmed. One of the most vivid and heartbreaking cases presented in this book is that of Brian Thomas, who in the grips of one of the night terrors he experienced throughout his life, mistook his wife for a burglar and strangled her to death. He was acquitted on the strength of expert testimony that those fight-or-flight responses that served out ancestors so well had betrayed Thomas most tragically.