The evolution of conditional moral assessment in indirect reciprocity

📝 Abstract

Indirect reciprocity is a major mechanism in the maintenance of cooperation among unrelated individuals. Indirect reciprocity leads to conditional cooperation according to social norms that discriminate the good (those who deserve to be rewarded with help) and the bad (those who should be punished by refusal of help). Despite intensive research, however, there is no definitive consensus on what social norms best promote cooperation through indirect reciprocity, and it remains unclear even how those who refuse to help the bad should be assessed. Here, we propose a new simple norm called “Staying” that prescribes abstaining from assessment. Under the Staying norm, the image of the person who makes the decision to give help stays the same as in the last assessment if the person on the receiving end has a bad image. In this case, the choice about whether or not to give help to the potential receiver does not affect the image of the potential giver. We analyze the Staying norm in terms of evolutionary game theory and demonstrate that Staying is most effective in establishing cooperation compared to the prevailing social norms, which rely on constant monitoring and unconditional assessment. The application of Staying suggests that the strict application of moral judgment is limited.

💡 Analysis

Indirect reciprocity is a major mechanism in the maintenance of cooperation among unrelated individuals. Indirect reciprocity leads to conditional cooperation according to social norms that discriminate the good (those who deserve to be rewarded with help) and the bad (those who should be punished by refusal of help). Despite intensive research, however, there is no definitive consensus on what social norms best promote cooperation through indirect reciprocity, and it remains unclear even how those who refuse to help the bad should be assessed. Here, we propose a new simple norm called “Staying” that prescribes abstaining from assessment. Under the Staying norm, the image of the person who makes the decision to give help stays the same as in the last assessment if the person on the receiving end has a bad image. In this case, the choice about whether or not to give help to the potential receiver does not affect the image of the potential giver. We analyze the Staying norm in terms of evolutionary game theory and demonstrate that Staying is most effective in establishing cooperation compared to the prevailing social norms, which rely on constant monitoring and unconditional assessment. The application of Staying suggests that the strict application of moral judgment is limited.

📄 Content

Sasaki T, Okada I, Nakai Y. 2017 The evolution of conditional moral assessment in indirect reciprocity. Sci. Rep. 7, 41870; doi:10.1038/srep41870 (published 2 February 2017).
Reprint is available from: http://www.nature.com/articles/srep41870

The evolution of conditional moral assessment in indirect reciprocity Tatsuya Sasaki1*, Isamu Okada2, Yutaka Nakai3 1Faculty of Mathematics, University of Vienna, Oskar-Morgenstern-Platz 1, Vienna, Austria 2Department of Business Administration, Soka University, 1-236 Tangi, Hachioji-city, Tokyo, Japan 3Faculty of Systems Engineering and Science, Shibaura Institute of Technology, Fukasaku 307, Minuma-ku, Saitama-city, Saitama, Japan *Correspondence to: tatsuya.sasaki@univie.ac.at Abstract Indirect reciprocity is a major mechanism in the maintenance of cooperation among unrelated individuals. Indirect reciprocity leads to conditional cooperation according to social norms that discriminate the good (those who deserve to be rewarded with help) and the bad (those who should be punished by refusal of help). Despite intensive research, however, there is no definitive consensus on what social norms best promote cooperation through indirect reciprocity, and it remains unclear even how those who refuse to help the bad should be assessed. Here, we propose a new simple norm called “Staying” that prescribes abstaining from assessment. Under the Staying norm, the image of the person who makes the decision to give help stays the same as in the last assessment if the person on the receiving end has a bad image. In this case, the choice about whether or not to give help to the potential receiver does not affect the image of the potential giver. We analyze the Staying norm in terms of evolutionary game theory and demonstrate that Staying is most effective in establishing cooperation compared to the prevailing social norms, which rely on constant monitoring and unconditional assessment. The application of Staying suggests that the strict application of moral judgment is limited.

2 Introduction How to get unrelated people to mutually cooperate is a fundamental issue in today’s highly mobile society. The last decades have seen researchers exploring indirect reciprocity, which is a major mechanism in the maintenance of cooperation between non-relatives1-10. The emergence of cooperation by indirect reciprocity can be summarized as, “I will help you if you have helped someone”10. Because helping is costly, however, self-interested recipients of help tend to freeload off others without further reciprocation, and unconditional cooperation is unlikely to evolve unless a specific supportive mechanism is provided11. Conditional cooperation, a main paradigm for exploring cooperation12, suggests that cooperation should be channeled to those who deserve help by using social network assessment systems, such as reputation or gossip media13-18. How should one assess others’ past behaviors? The simplest social norm, called Scoring, assesses those who give and refuse to give help as good and bad, respectively19,20. This norm depends only on individuals’ previous actions. Since the seminal study of Nowak and Sigmund10, Scoring has been investigated in terms of evolutionary game theory, primarily using a donor–recipient giving game. Unconditionally applying the Scoring norm raises a key question: Is it morally or socially acceptable to refuse to help someone with a bad image? This point is Scoring’s Achilles’ heel in the typical good-or-bad binary system10. By definition, when a discriminator refuses to help a potential opponent with a bad image, the discriminator’s image decisions become clouded. Thus, in the Scoring norm, a bad image is contagious. Although helping can redress the discriminator’s image, a bad image may cause the discriminator to undergo rejection by other discriminators. Even slight involuntary errors can damage a discriminator’s image and thus payoff. The Scoring norm, therefore, results in the mutual defection of all players21,22; this is referred as the “Scoring dilemma.” To address this dilemma, social norms have been developed that distinguish between justified and unjustified defection by accounting for the recipient’s image1. In the case of a bad recipient being refused help, such refusal should not damage the donor’s image (i.e., justified defection)1,21,22. Indeed, the top eight social norms, identified from 4,096 candidate strategies by

3 systematic research (called the “leading eight”)23,24 share a common relevant feature—if a good donor refuses to help a bad recipient, the donor is assigned a good image (see Table S1). Although the leading social norms are highly sophisticated, they are thus cognitively costly. Indeed, all of the leading eight rely on (i) the donor’s last action and (ii) the recipient’s last image (i.e., second-order social norms), and six of them also rely on (iii) the donor’s last image (i

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