at maximizing their food intake. So he cut up some white bread into precisely weighed pieces and enlisted some friends to toss the pieces onto the pond.

The ducks, naturally, were delighted with this experiment, so they all rapidly paddled into position. But then Harper’s helpers began tossing the bread onto two separated patches of the pond. At one spot, the bread tosser dispensed one piece of bread every five seconds. The second was slower, tossing out the bread balls just once every 10 seconds.

Now, the burning scientific question was, if you’re a duck, what do you do? Do you swim to the spot in front of the fast tosser or the slow tosser? It’s not an easy question. When I ask people what they would do, I inevitably get a mix of answers (and some keep changing their mind as they think about it longer).

Perhaps (if you were a duck) your first thought would be to go for the guy throwing the bread the fastest. But all the other ducks might have the same idea. You’d get more bread for yourself if you switched to the other guy, right? But you’re probably not the only duck who would realize that. So the choice of the optimum strategy isn’t immediately obvious, even for people. To get the answer you have to calculate a Nash equilibrium.

After all, foraging for food is a lot like a game. In this case, the chunks of bread are the payoff. You want to get as much as you can. So do all the other ducks. As these were university ducks, they were no doubt aware that there is a Nash equilibrium point, an arrangement that gets every duck the most food possible when all the other ducks are also pursuing a maximum food-getting strategy.

Knowing (or observing) the rate of tosses, you can calculate the equilibrium point using Nash’s math. In this case the calculation is pretty simple: The ducks all get their best possible deal if one-third of them stand in front of the slow tosser and the other two-thirds stand in front of the fast tosser.

And guess what? It took the ducks about a minute to figure that out. They split into two groups almost precisely the size that game theory predicted. Ducks know how to play game theory!



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