Collective action and the collaborative brain

Abstract

Humans are unique both in their cognitive abilities and in the extent of cooperation in large groups of unrelated individuals. How our species evolved high intelligence in spite of various costs of having a large brain is perplexing. Equally puzzling is how our ancestors managed to overcome the collective action problem and evolve strong innate preferences for cooperative behaviour. Here, I theoretically study the evolution of social-cognitive competencies as driven by selection emerging from the need to produce public goods in games against nature or in direct competition with other groups. I use collaborative ability in collective actions as a proxy for social-cognitive competencies. My results suggest that collaborative ability is more likely to evolve first by between-group conflicts and then later be utilized and improved in games against nature. If collaborative abilities remain low, the species is predicted to become genetically dimorphic with a small proportion of individuals contributing to public goods and the rest free-riding. Evolution of collaborative ability creates conditions for the subsequent evolution of collaborative communication and cultural learning.

Figure 1.

Collective action in ‘us versus nature’ games. Each figure shows the effects of four parameters (benefit of collaboration b, cost of individual effort c, cost of collaborative ability s and the group size n) on the average equilibrium values of individual effort x (first column) and collaborative ability α (second column). (a,b) Relatively low individual effort is required for the production of public goods (‘half-saturation’ parameter X₀ = 0.25n). (c,d) Relatively high individual effort is required for the production of public goods (‘half-saturation’ parameter X₀ = 0.5n). In most cases, individual effort x does not evolve and the collaborative ability α remains close to the baseline level of θ = 0.4. The height of the bars is also reflected in their colour using the jet colormap in Matlab (low values in dark blue and high values in brown).

Figure 2.

Collective action in ‘us versus nature’ games. Each figure shows the effects of four parameters (benefit of collaboration b, cost of individual effort c, cost of collaborative ability s and the group size n) on (a) average individual effort at equilibrium x, (b) collaborative ability α and (c) within-group standard deviation in individual efforts. The baseline collaborative ability θ = 0.4. The height of the bars is also reflected in their colour using the jet colormap in Matlab (low values in dark blue and high values in brown).

Figure 3.

Evolution of individual efforts and collaborative ability in ‘us versus them’ games. (a) High cost of collaborative ability s (=0.4) results in low collaborative ability α and bimodal distribution of individual efforts x. (b) Intermediate cost of collaborative ability s (=0.2) results in the evolution of high collaborative ability α and high average efforts x . Other parameters: group size n = 8, benefit of collaboration b = 1, cost of individual effort c = 1 and the baseline collaborative ability θ = 0.2. The intensity of the black colour is proportional to the number of individuals with the corresponding trait values. Red lines show the mean values.