Experimental Results in the Boxed-Pigs Game
Experimental Results in the Boxed-Pigs Game. The Graphs Record the Average Number of Presses of the Lever (After 10 Trials) During a 15-Minute Period by Dominant and Subordinate Animals After 24 Hours Without Food when Tested (a) Separately and (b) Together
0 1 5 10 105 Tests
(a) (b)
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3.4 Solving a Game when Rationality Is Common Knowledge 73
number. Up through trial 10, the pigs were in separate cages and the dominant pig pressed the lever slightly more. Starting with trial 10, they were placed in the same cage—and the results are striking: the dominant pig increasingly was the one to press the lever.
I am not claiming that the pigs achieved this outcome by each pig thinking about what the other pig was think- ing. A more likely explanation is that they got to it through trial and error. Indeed, note that their behavior gets closer and closer to the predicted outcome over time. Perhaps a few times in which the submissive pig presses the lever and ends up with nothing but crumbs could well induce it to stop pressing the lever, and at that point, the dominant pig learns that the only way it’ll eat anything is if it presses the lever. Experience can be a substitute for clever reasoning.