When it comes to computing efficiency, humans beings blow Watson away. As Jonah Lehrer points out, the human brain requires with less power than a dim light bulb. Watson, as it labors to replicate only one function of the brain--question-answering--heats up a room full of computers, and needs a bank of roaring air-conditioners to keep them from melting. There's no contest.

But the efficiency of the human brain won't prevent machines like Watson from encroaching on certain jobs, starting with call centers. First, these computers will grow dramatically more efficient. That's the nature of information technology. Not too long ago, generating the computing power in an iPhone also used to require a roomfull of hot machinery. The other point is this: While human brains are efficient, we consume a lot more energy than that single lightbulb. We drive cars, we heat and cool our houses, we eat food from all over the world. From a company's perspective, operating a human, at least in this country, costs tens of thousands of dollars a year. When it comes to efficiency, they'll be comparing the cost of the entire human being to Watson. We're far more than our magnificent brains, and we cost more, too.