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.

Scientists often talk of parsimony (as in "the simplest explanation is probably correct," also known as Occam's razor), but we should not get seduced by the apparent elegance of argument from parsimony; this line of reasoning has failed in the past at least as many times as it has succeeded.

If our brains were simple enough to be understood, we wouldn't be smart enough to understand them.

Who you are depends on the sum total of your neurobiology.

Societies would _not_ be better off if everyone were like Mr Spock, all rationality and no emotion. Instead, a balance - a teaming up of the internal rivals - is optimal for brains. ... Some balance of the emotional and rational systems is needed, and that balance may already be optimized by natural selection in human brains.

In my view, the argument from parsimony is really no argument at all - it typically functions only to shut down more interesting discussion. If history is any guide, it's never a good idea to assume that a scientific problem is cornered.

All life is no more than a match struck in the dark and blown out again.