If you have certain problems with your brain but are raised in a good home, you might turn out okay. If your brain is fine and your home is terrible, you might still turn out fine. But if you have mild brain damage and end up with a bad home life, you're tossing the dice for a very unlucky synergy.

The missing crowds make you lonely. You begin to complain about all the people you could be meeting. But no one listens or sympathizes with you, because this is precisely what you chose when you were alive.

It turns out that dopamine is a chemical on double duty in the brain. Along with its role in motor commands, it also serves as the main messenger in the reward systems, guiding a person toward food, drink, mates, and all things useful for survival. Because of its role in the reward system, imbalances in dopamine can trigger gambling, overeating, and drug addiction - behaviors that result from a reward system gone awry.

Many people prefer a view of human nature that includes a true side and a false side - in other words, humans have a single genuine aim and the rest is decoration, evasion, or cover-up. That's intuitive, but it's incomplete. A study of the brain necessitates a more nuanced view of human nature.

This is what consciousness does: it sets the goals, and the rest of the system learns how to meet them.

The first thing we learn from studying our own circuitry is a simple lesson: most of what we do and think and feel is not under our conscious control.

It is the most wondrous thing we have discovered in the universe, and it is us.