It’s hard to conceive offhand of a less promising consumer innovation than a computer that comes factory equipped with “emotions”—but here’s a candidate: how about a “spiritual” computer? The spiritual computer spends its time pondering the mysteries of the universe, occasionally printing cryptic messages on its screen and otherwise ignoring the user altogether.

Here’s what the “emotional” computer would do. You might describe a complicated medical case to it and ask for the diagnosis. The computer might give you a serious, telling answer, but add, “...still, I’m not happy with that; it doesn’t feel right.”

You might describe a complex legal case and ask for its advice. It’s answered harder questions before, but on this occasion it might put you off with a comment about how the plaintiff reminds it of your sister.

You might describe an intricate stock deal and ask whether you should invest. In the past its advice has been solid—not infallible but better than any human’s you’ve ever consulted, in part because it has billions of case histories down cold. But on this occasion it tells you, “Buzz off. I’m not in the mood. Let’s talk about Jane Austen.”

Who needs this kind of nonsense from a computer? Science does; in a broader sense we all do, because adding “emotions” to computers is the key to the biggest unsolved intellectual puzzle of our time: how thinking works&