How to get moral "free-riders" to cooperate

What motivates people to contribute to trustful moral judgment, which is a public good yet tends to be costly? This is "the moral free rider problem". Mathematician Tatsuya Sasaki from University of Vienna and colleagues Isamu Okada and Yutaka Nakai in Japan have put forth a theoretical resolution. The study has been published online in Biology Letters, a journal published by The Royal Society.

A trustful moral judgment system of good or bad is the building block of cooperation in a large group. A rule of thumb for promoting cooperation is to help those who have a good reputation and not those who have a bad reputation. However, making trustful moral judgment requires time, effort and money. Therefore, this raises a crucial issue – the moral free riders who evade the cost associated with moral judgment (e.g. by not paying taxes for police and court) are better off than those who shoulder the cost. Recent years have seen game theoreticians considering voluntary reactive policing of the moral free riders, which is costly, too, and thus can be exploited by higher order moral free riders. This leads to an infinite regress of opportunities to free ride. The moral free rider problem has remained unsolved.

In this paper, Tatsuya Sasaki, Isamu Okada (Soka University, Tokyo) and Yutaka Nakai (Shibaura Institute of Technology, Saitama) have taken a different approach. The authors present a simple and broadly applicable solution that considers a pre-assessment of the moral free riders. Sasaki and his colleagues devise an extra assessment system that offers an option to contribute to a pool account of the moral cost in advance. This is aimed not only at funding but also at detecting and labelling those who are not willing to pay for justice prior to the social exchange. In social exchanges, the labelled individuals will be refused help. Through game-theory analysis, this study finds that pre-assessment leads to stabilizing a costly moral system and thus cooperation.

This has an important implication to contemporary issues. How good and bad are determined, in fact, varies among individuals with different moral standards. Sasaki and his colleagues show that the pre-assessment could be the common feature for sustaining the moral system, irrespective of its moral code. "Our findings suggest that different individuals may not agree on what justice is but may arrive at a consensus about how justice is maintained.  The results of future work that investigates to what extent the pre-assessment affects moral diversity will be fascinating", says Sasaki.

Publication in the Royal Society journal "Biology Letters":
Sasaki T, Okada I, Nakai Y. 2016. Indirect reciprocity can overcome free-rider problems on costly moral assessment. Biology Letters 12: 20160341.
http://dx.doi.org/10.1098/rsbl.2016.0341