Satoshi Kanazawa

The Scientific Fundamentalist

Why Do We Believe in God?

The connection between God and Beavis and Butt-head.

Posted Mar 24, 2008

Answer: Beavis and Butt-head.

Good night, everybody! Drive home safely, and don’t forget to tip your waitress!

Trust me, this connects....

Imagine a typical scene in Beavis and Butt-head, on a rare occasion when the boys are not sitting on the couch watching videos. (I haven’t watched MTV since 1994, so I hope their show is still on; otherwise, I might as well be talking about Uncle Miltie and the Texaco Star Theater.) So Beavis and Butt-head are walking down the street, and pass a couple of young, attractive women, dressed in their obligatory tank tops and hot pants. As the women pass, one of them turns to Beavis and Butt-head, smiles, and says “Hi!”

Now what happens? Beavis and Butt-head freeze, their entire cognitive functions (such as they are) on hold, and they mutter, “Whoa.... She wants me.... She wants to do it.... I’m gonna score....”

Whether you are a man or a woman, if you think about your own life for a minute, you’ll soon realize that this is a very common occurrence. A man and a woman meet and engage in a friendly conversation. After the conversation, the man is convinced that the woman is attracted to him and perhaps wants to sleep with him, when the woman is entertaining no such thought; she’s just being nice and friendly. It is a common theme of many romantic comedies (as well as virtually every episode of Three’s Company.... Am I dating myself?) Why does this happen?

Haselton and Nettle’s Error Management Theory offers a very convincing explanation. Their theory begins with the observation that decision making under uncertainty often results in erroneous inference, but some errors are more costly in their consequences than others. Evolution should therefore favor an inference system that minimizes, not the total number of errors, but their total costs.


For example, in the case at hand, the man must decide, in the absence of complete information, whether the woman is romantically interested in him or not. If he infers that she is when she is in fact interested, or if he infers that she is not when she is in fact not interested, then he has made the correct inference. In the other two cases, however, he has made an error in inference. If he infers that she is interested when she is in fact not interested, then he has made an error of false positive (what the statisticians call the “Type I” error). In contrast, if he infers that she is not interested when she is in fact interested, then he has made an error of false negative (what the statisticians call the “Type II” error). What consequences do the false positive and false negative errors entail?

If he made the error of inferring she’s interested when she’s not, then he’d come on to her but ends up being rejected, laughed at, and possibly slapped in the face. If he made the error of inferring she’s not interested when she is, then he’d missed an opportunity for sex and possible reproduction. As bad as being rejected and laughed at is (and, trust me, it is), it is nothing compared to missing a genuine opportunity for sex. So, Haselton and Nettle argue, evolution has equipped men to overinfer women’s romantic and sexual interest in them, so that, while they may make a large number of false-positive errors (and, as a result, get slapped all the time), they would never miss a single opportunity for sex.

Among engineers, this is known as the “smoke detector principle.” Just like evolution, engineers build smoke detectors in order to minimize, not the total number of errors, but their total costs. The consequence of a false-positive error of a smoke detector is that you’re woken up at three o’clock in the morning by a loud alarm when there is no fire. The consequence of a false-negative error is that you and your entire family are dead when the alarm fails to go off when there is a fire. As unpleasant as being woken up in the middle of the night for no reason may be, it’s nothing compared to being dead. So the engineers deliberately make smoke detectors to be extremely sensitive, so that it will give a lot of false-positive alarms but no false-negative silence. Haselton and Nettle argue that evolution, as the engineer of life, has designed men’s inference system similarly.

So that’s why men always come on to women and make unwelcome passes all the time. But what in God’s name does any of this have to do with our belief in God? I’ll explain in my next post. Trust me, this connects.