Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.

Altruists and envious people who meet in contests are symbionts. They do better than a population of narrowly rational individuals. If there are only altruists and envious individuals, a particular mixture of altruists and envious individuals is evolutionarily stable.

We study the impact of advice or observation on the depth of reasoning in an experimental beauty-contest game. Both sources of information trigger faster convergence to the equilibrium. Yet, we find that subjects who receive naive advice outperform uninformed subjects permanently, whereas...