Rawlsian altruism with perfect discrimination leads to social efficiency

ABSTRACT

Recent studies draw attention on the highly specialized capacity of human beings in recognizing altruists versus cheaters in social interactions. These results hint at the existence of specialized abilities that support discriminating behavior in strategic interactions. In this paper, we explore the implications of discriminating behavior in the study of the indirect evolutionary selection of selfish versus altruistic motivations in the context of generic 2×2 base games, and in particular for coordination and cooperation scenarios. We find that inequality averse (Rawlsian) altruism can enforce under rather general conditions socially optimal outcomes, including cases where selfishness cannot, such as in prisoner’s dilemmas. Inequality seeking (Nietzschian) altruism in no case improves upon Rawlsian altruism in terms of social optimality of outcomes, and often does worse. In the cooperation scenario in particular, Nietzschean altruism never manages to implement the cooperative outcome. Under perfect discrimination, moreover, inequality averse (Rawlsian) altruism often evolves at the expense of selfishness. These results suggest that the development of sophisticated discrimination abilities may be strongly adaptive in supporting fairness-oriented forms of pro-sociality in humans in the context of social dilemmas and coordination problems.

KEYWORDS:

• Cooperation
• coordination
• perfect discrimination
• Rawlsian altruism
• replicator dynamics

Acknowledgment

We thank the editor and two anonymous referees for useful comments and suggestions on an earlier draft. The usual disclaimer applies.

Notes

¹ In the whole paper we will consider only symmetric NE when dealing with a symmetric game (like ).

² Games in which B is strictly dominant, which occurs if a < c and b < d, yield analogous results.

³ Obviously, assuming a > d would be restrictive for dominance solvable games since it would rule out games like the prisoner’s dilemma, in which the reverse inequality d > a holds.

⁴ Even though the base game is 2 × 2, we are dealing with n × n games as in next section we will consider 4 × 4 games.

⁵ A proof of Lemma 1(ii) can be found in Menicucci and Sacco (2009).

⁶ Menicucci and Sacco (2009) refer to noncooperative players as best-reply players as in Banerjee and Weibull (1995). We speak of selfish players to emphasize the motivational dimension.

⁷ Dynamics over boundary faces is obtained deleting the strategies that do not belong to the face considered. They are easily derived and the task is left to the reader.

⁸ Binmore and Samuelson (1992) obtain an analogous result in the relatively different context of evolutionary games with finite automata.

⁹ Proposition 8(3) in Menicucci and Sacco (2009) is stated for a = 1 and d = 0, but that is just a normalization with no qualitative effect on results. The same remark applies to our reference to Proposition 8(ii) in Menicucci and Sacco (2009), below in this subsection.

¹⁰ I.e., the altruistic attitude is not conditional upon whether or not the opponent belongs to the same (RA) type.