The Power of Habit

by Charles Duhigg
Random House, $28.00 
274 pages

The basal ganglia is a golf ball-sized lump of tissue in the brain, the importance of which was not well understood until the early 1990s. It was then that a team of scientists at Massachusetts Institute of Technology noticed that rats with impaired basal ganglia developed problems with tasks such as remembering how to open food containers.

By surgically implanting tiny sensors into the test animals' brains, the scientists were able to track the way the brain responded as rats hunted for chocolate in a labyrinth. There were no set patterns of behavior as the rats sniffed out the chocolate. To the casual observer, it appeared as if the animals were idly meandering about. The electronic sensors told a different story, however: the rodents' brains were working furiously as they navigated the maze.