Most of us are “irrationally” afraid of snakes…but few of us are afraid of mushrooms. Since both can be potentially fatal and both can be good eating, this is puzzling.

That’s from “Information, Evolution and Utility,” a paper by Jeroen Swinkels and Larry Samuelson about why natural selection shaped our preferences the way it did.  In their story, Nature accepts that there are things that we can learn that she hasn’t had time to program into us (like which mushrooms are safe to eat.)  So instead of giving us a complete set of instructions for how to behave in every situation, she gave us beliefs and the instinct to experiment and learn.  Then she lets us choose.

But there are somethings she knows better than us .  For example that snakes will likely kill us.  So, forseeing that these beliefs she has given us can, and often do, go astray, she builds in backup measures to stop us from acting on them in contexts where she is confident that she knows best. Hence irrational fears.

I think there is wide open arbitrage opportunity in behavioral economics to import ideas from principal-agent theory to explain why Nature (the principal) has given us (the agent) certain preferences (incentives.)