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Robert Kurzban

The Evolutionary Psychology Blog

By Robert Kurzban

Robert Kurzban is an Associate Professor at the University of Pennsylvania and author of Why Everyone (Else) Is A Hypocrite. Follow him on Twitter: @rkurzban

Jack, Jill, and a Lion

Published 9 November, 2010

Once upon a time, Jack and Jill found themselves on an island. Every day, each of them had to decide whether to go into the forest to pick fruits, which were good for them and they liked very much, or stay by the beach and dig up tubers, which were starchy, bland, and had few nutrients. The problem was that sometimes a lion roamed the forest, making it more dangerous. So, while the fruits were tastier and more nutritious, collecting them came with a risk.

Now, since this is just a story, we’ll make the forest magical. Whenever the lion was in the forest, the leaves of the trees turned blue.

Now Jill, being clever, used a very simple method to choose when to go picking fruit in the forest. She only went when the leaves were green, meaning the lion was elsewhere. So, Jill sometimes got fruit, and sometimes had to settle for tubers, but never got eaten by a lion.

Jack, however, was even more clever than Jill. He was so clever, he decided to believe, incorrectly, that the leaves were always blue, and that the lion was always in the forest. So, he never went picking fruit, and had to settle for tubers all the time.

What’s wrong with this story is, obviously, that Jack isn’t clever at all. In fact, if Jack and Jill reproduced asexually, clearly Jill would leave more offspring, being nourished by fruits as opposed to just tubers. Jack is very obviously at a severe competitive disadvantage.

Ok, that’s really clear, but my point really has to do with this argument in the context of a recent article in the Globe and Mail which reports on some interesting research by Jesse Bering. The upshot of the work is that people who think that a supernatural agent is observing them don’t cheat as much. Bering’s argument, which he’s made elsewhere, is that belief in supernatural agents is evolutionarily advantageous because these beliefs make you less likely to cheat.

I am very fond of the people who have been making this argument, but I confess it seems illogical on the face of it. Just like Jack, who doesn’t take advantage of picking fruits when there’s no lion about, people with false beliefs about being observed and punished by supernatural entities don’t take advantage of the opportunities they would have if they didn’t have their incorrect beliefs. (I’m assuming that supernatural agents don’t exist, and, even if they did, that they punish people only after the person in question has had whatever reproductive success they’re going to have, making punishment in the afterlife irrelevant in the fitness sense.) It’s good, not bad, in the evolutionary sense, to cheat if the expected value of cheating is higher than the expected value of not cheating in the same way that it’s good, not bad, to go picking fruit when the lion sleeps tonight or whatever.

I do not see any way around this problem. The idea that believing in supernatural agents is an advantage because it causes you to make worse decisions doesn’t make any sense to me. Very generally, false beliefs tend to be bad for good decision making. But then, maybe it all makes sense if you read the book

  • Melissa

    I dunno, I wrote a paper once on the economics of religious belief in Central Africa and while some of beliefs were cruel/completely incompatible with modern development goals, I could see how they could be adaptive in a primitive environment. In fact there was one regarding a certain root and how you’d anger the forest gods if you took too much. Turns out it has some toxic compound, but is safe under a certain threshold.

  • http://www.blogger.com/profile/10546265581296919974 Rob

    Doesn’t dual-inheritance theory resolve the problem?

    • Robert Kurzban

      Thanks for the comments. What I’m saying here is not that there is no explanation for supernatural beliefs. (In fact, I have also argued that they are commitment devices, though my argument is slightly different; I didn’t know about the paper linked in the second comment, so thanks.) My point here is narrowly the logic of this line of argument about the putative value of mistakenly believing all actions are observed (and so potentially punished).

  • Nick

    I agree somewhat, but wouldn’t the benefit of cheating behavior depend on the context? ‘Cheating’ to immediately gain a strategic advantage is one thing, but what about the more distal consequences? To use Bering’s example, children/adults who don’t cheat because they fear a supernatural ‘watcher’ are more likely to play fair, and it’s not too hard to imagine the selective benefits there. That is, if it outweighs the immediate benefit you get from cheating…

    • Rob Kurzban

      I agree that the benefit of cheating depends on context. Jill, to use my example, takes into account the true costs of cheating (the chance of getting caught, the reputation benefits of playing fair). The comparison has to be between an agent taking account of context and another agent taking account of context and in addition taking account of supernatural agents. Simply not taking account of supernatural agents doesn’t mean always cheating independent of the costs, benefits, and context.

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