Four levers of reciprocity across human societies: concepts, analysis and predictions

Abstract

This paper surveys five human societal types - mobile foragers, horticulturalists, pre-state agriculturalists, state-based agriculturalists and liberal democracies - from the perspective of three core social problems faced by interacting individuals: coordination problems, social dilemmas and contest problems. We characterise the occurrence of these problems in the different societal types and enquire into the main force keeping societies together given the prevalence of these. To address this, we consider the social problems in light of the theory of repeated games, and delineate the role of intertemporal incentives in sustaining cooperative behaviour through the reciprocity principle. We analyse the population, economic and political structural features of the five societal types, and show that intertemporal incentives have been adapted to the changes in scope and scale of the core social problems as societies have grown in size. In all societies, reciprocity mechanisms appear to solve the social problems by enabling lifetime direct benefits to individuals for cooperation. Our analysis leads us to predict that as societies increase in complexity, they need more of the following four features to enable the scalability and adaptability of the reciprocity principle: nested grouping, decentralised enforcement and local information, centralised enforcement and coercive power, and formal rules.

Keywords: Human evolution; cooperation; large-scale societies; law; reciprocity; rules.

Graphical abstract

Figure 1.

Folk Theorem for two-players' situation (adapted from Fig. 1 of Binmore (2014); we suggest Binmore (2007) and Seabright (1993) as accessible and lively accounts of the Folk theorem and Mailath and Samuelson (, pp. 33, 193, 232) for in-depth general treatments). The whole region (white and orange) below the curve joining the two axes represents the set of payoff pairs available to two players as the outcomes of a given action situation. The shaded region (orange) displays the pairs of average payoffs available as mixed-strategy Nash equilibria in the repeated version of the action situation (Nash equilibria of the game defined by eqn (1) of Box 1) and thus displays a multiplicity of equilibria available to the players that are compatible with the incentive structure of the action situation under focus. Three types of such Nash equilibria in this region are noteworthy. First, the inefficient equilibrium or reservation payoff to individuals obtained as the best then can do given others inflict the worst on them (i.e. the state of “war of all against all”). Second, the whole upper boundary of the orange region, which is a line of efficient equilibria where no individual can have its payoff increased without making the other player worse off. Finally, the fair equilibrium. Exactly the same logic applies mutatis mutandis to n-player interactions (see Box 1), with the only change being the dimensionality of the sets of the various equilibria. The Folk theorem says nothing about which equilibrium in the orange region obtains and this depends on how individuals organize the play of the action situation under focus. Interactions between a large number of unrelated and disorganized individuals is likely to result in the selection of an equilibrium close to the inefficient one: think of strangers attempting to construct a common irrigation system, but who lack any communication or coordination devices. As such, systems of group governance, where individuals structure their own interaction by way of devising rules of interactions - institutions - can favour more efficient equilibria (Ostrom, ; Gardner and Ostrom, ; Powers et al., 2016). This will push the system towards the efficient equilibrium region (arrows pointing upward). This region nonetheless still allows for very unequal resource distributions, but the present paper is not concerned with fairness or inequality issues (see Binmore, , 2014 for considering such issues).