Excerpt from Us and Them by David Berreby, plus links to reviews, author biography & more

You also use human kinds to understand yourself. That means they must link to the brain's systems for monitoring the body, both inside and outside of your conscious awareness. "I feel tired and achy because I have been working hard" is a statement that combines your mind's reports on your mood and bodily state with memories and thoughts about cause and effect. "I get my self-reliance from my pioneer ancestors" is the same kind of multi-process report, which relates your sense of yourself to your knowledge of cause and effect.

There are other ways in which thoughts and feelings about human kinds must involve a general-purpose mental machine, applied to the particular problem of understanding others. For example, people tend to treat nonhuman things as if they were human. We say cancer is a cruel disease, as if cancer had a personality; we yell at the crashed computer, as if it decided to ruin our file. Whether or not it can be true, we assume that things happen as the result of thoughts and moods in the minds of other beings. When people do the same thing to a tribe, as when they say, "America is arrogant," or "Buddhists are gentle," they're applying this general-purpose habit to human kinds. The mind also is equipped with a predisposition to understand other people and to get along with them. We attach this ability to team up with others to our sense of human kinds. We decide that someone is trustworthy not because we know him but because "he's a Mormon" or "she's a surgeon." There, too, we're applying a general habit to the special realm of human kinds.

So it's not too surprising that football fandom and race and nationality and religion can be talked about with the same words. These human-kind perceptions have different fates in society, but they come from shared pathways in the mind.

Yet that doesn't explain why people, unlike other creatures, have such elaborate categories for one another. Robins are a kind of bird, and Christians are a kind of person, and so those two concepts must share categorizing processes in the brain. But the category "Christians" also taps emotions and thoughts that don't arise when classing birds. It's likely, then, that there's a second major reason all human kinds feel alike: they draw on a special piece of the mind, which is dedicated only to them.

What might this special human-kind maker be like? One safe bet is this: it is not based on the rules of logic. It works outside of awareness, according to rules of its own. It is not at all like the rigorous study of causes and effects that people call science.

After all, much of what people say about human kinds is, as a matter of measurable fact and logic, meaningless. A soccer fan says, "We have a good chance of getting to the playoffs," but he'll have no effect on the matches, because he isn't on the team. A corporate spokesman says, "We're sorry that our product was defective," though he had nothing to do with making or marketing it. An African American preacher says, "We came to this continent as slaves," yet neither he nor anyone he knows was ever in shackles. A devout Shiite weeps and flagellates himself in grief on the tenth of Muharram for the death of Imam Hussein at Karbala; but that martyrdom took place more than thirteen hundred years ago, in the year 680 C.E., and no one alive today could have seen it.

Copyright © 2005 by David Berreby.  No part of this book maybe reproduced without written permission from the publisher.