Subtitles section Play video Print subtitles >>Charles Duhigg: So about a decade ago there was a woman named Dr. Ann Graybiel at MIT who is a neurologist, and for years she had been doing experiments to try and get sensors into the craniums of rats so she could measure what was going on inside their heads as they went about their daily business. As you can imagine it took a long time and a lot of rats to figure out how to do this, but eventually she got to a point where she could get about 150 sensors into a rat's cranium. And she would do the same thing with every single rat. After the surgery she would take them and put them in the world's simplest maze. This maze works the same way every single time. There's a click, the partition moves and the fat is free to move up and down. Now if anyone has ever done this with a rat, what you know is when you drop a rat in a maze like this it looks like the world's stupidest animal. The rat will run up and down the center aisle and sniff and scratch. When it gets to the end it will actually see the chocolate and then go the opposite direction. This is actually one of the reasons why rats are used in experiments is because it's considered that if you can teach a rat something you must be able to teach any animals anything. So she would do this experiment, but for the first time she was able to see what was going on inside the rat's head. This is a simplified neurological graph of the first time that a rat is dropped in this maze. What you will notice is that its brain is actually working hard the entire time. So when the rat would scratch on the walls, the scratching centers would light up, when it would sniff, the sniffing centers would light up. It's actually trying to process as much information as possible. This is what learning looks like. So Dr. Graybiel takes the rats, each one, and drops them in 100, 150 times. And as imagine, over time the rats learn how to navigate through the maze faster and faster. Click, the partition moves, the rat will make a beeline to the chocolate and it actually becomes a habit. But what's really interesting is Dr. Graybiel sees for the first thing what is going on inside the rat's cranium. As the rat gets faster and faster, as the habit to find the chocolate becomes stronger and stronger, the rat essentially thinks less and less and less. This graph at the bottom is a simplified neurological graph of the 150th iteration of a rat running through a maze. And that dip you see right there is the same dip that you would see if a rat went to sleep. There was a scientist at Duke University a couple of years ago who did a study to try and figure out how much of your day was habits. She followed a bunch of people around and found that 40 to 45% of the actions we take everyday aren't really behaviors. They're actually just habits. And if I could somehow stick 150 sensors into your head which I would not recommend, then when I saw you backing your car out of your driveway or walking down the hall muttering to yourself or making automatic decisions, I would see your brain looking like this. But what's interesting is if you notice there's these two spikes in neurological activity. When there's the click we see a burst of neurological activity and then essentially the brain almost goes to sleep. Then the rat finds the chocolate and it's if as the brain sort of wakes itself up again to pay attention to what's going on. This is the neurological signature of a habit.