Cooperating with the future

Journal name:
Nature
Volume:
511,
Pages:
220–223
Date published:
DOI:
doi:10.1038/nature13530
Received
Accepted
Published online

Overexploitation of renewable resources today has a high cost on the welfare of future generations1, 2, 3, 4, 5. Unlike in other public goods games6, 7, 8, 9, however, future generations cannot reciprocate actions made today. What mechanisms can maintain cooperation with the future? To answer this question, we devise a new experimental paradigm, the ‘Intergenerational Goods Game’. A line-up of successive groups (generations) can each either extract a resource to exhaustion or leave something for the next group. Exhausting the resource maximizes the payoff for the present generation, but leaves all future generations empty-handed. Here we show that the resource is almost always destroyed if extraction decisions are made individually. This failure to cooperate with the future is driven primarily by a minority of individuals who extract far more than what is sustainable. In contrast, when extractions are democratically decided by vote, the resource is consistently sustained. Voting10, 11, 12, 13, 14, 15 is effective for two reasons. First, it allows a majority of cooperators to restrain defectors. Second, it reassures conditional cooperators16 that their efforts are not futile. Voting, however, only promotes sustainability if it is binding for all involved. Our results have implications for policy interventions designed to sustain intergenerational public goods.

At a glance

Figures

  1. An illustration of the Intergenerational Game (IGG).
    Figure 1: An illustration of the Intergenerational Game (IGG).

    In each generation, a group of 5 people makes a decision (individually or according to an institutional rule) about their level of extraction from a common resource. a, If Generation 1’s extractions do not violate the commonly known threshold, the resource refills and the same dilemma is presented to Generation 2. After each generation, another generation occurs with probability δ. b, If at any point the threshold requirement is not met, the resource does not renew and future generations receive no payoff. Maximal social welfare is achieved if no generation ever violates the threshold requirement by extracting too much from the common resource.

  2. Solving the (intergenerational) /`tragedy of the commons/' through an institutional design.
    Figure 2: Solving the (intergenerational) ‘tragedy of the commons’ through an institutional design.

    a, When decisions are made at the individual level, the availability of the common pools drastically decreases over time; n = 480. b, The introduction of a democratic voting institution strikingly improves sustainability; n = 370. c, Decreasing the discount factor from δ = 0.8 to δ = 0.7 (n = 355) or δ = 0.6 (n = 305) while holding T = 50%, or the extraction threshold from T =  50% to T =  40% (n = 600) or T = 30% (n = 460) while holding δ = 0.8, increases the temptation to defect. Nonetheless, much less is extracted under median voting compared to the unregulated baseline. Error bars indicate standard errors of the mean.

  3. The voting institution is robust to extreme decision-makers and thereby increases cooperative behaviour.
    Figure 3: The voting institution is robust to extreme decision-makers and thereby increases cooperative behaviour.

    a, The pivotal decision-maker in the voting institution is different from the unregulated institution. For instance, assume that T =  50% and that a cooperator and a defector always extract 10 and 20 units, respectively. The unregulated institution is vulnerable to extreme decision-makers, whereas the voting institution is robust to a minority of defectors. This, in turn, bolsters the decision of those who are predisposed towards cooperation but fear to be exploited (for example, future-oriented ‘conditional cooperators’). b, This leads to an increase of cooperators in the voting institution (n = 370) over the unregulated institution (n = 480).

  4. Voting must be binding for all players in order to achieve high levels of sustainability.
    Figure 4: Voting must be binding for all players in order to achieve high levels of sustainability.

    a, In a partially implemented voting institution (n = 495), three of the individuals are bound to a vote while the other two can extract at will. A partially implemented voting institution is not robust to a minority of defectors and also cannot reassure conditional cooperators. Thus, partial voting fails to lead to sustainable outcomes. b, Three real sets of decisions from our data demonstrate a consequence of the pivotal extractor outside the voting group.

  5. Bootstrapping simulations demonstrate the robustness of full voting and the failure of partial voting.
    Extended Data Fig. 1: Bootstrapping simulations demonstrate the robustness of full voting and the failure of partial voting.

    We address sources of noise in the sequence of events that occurred in our experiment by conducting a set of computer simulations using the data generated by our participants. We randomly sample (with replacement) a series of generations of participant decisions, and calculate the fraction of those generations in which the pool was refilled. For each condition, we simulate 10,000 pools (or 1,000,000 pools if δ < 0.8) for 15 generations. a, Simulated data for the unregulated, full voting and partial voting conditions show that full voting is by far the most successful at sustaining the pool. b, Simulated data for the T = 40%, T = 30%, δ = 0.7 and δ = 0.6 conditions shows that reducing δ has only a small effect, and although reducing T does undermine sustainability, the effect is much less striking than that of unregulated or partial voting despite the higher value of T in these less-regulated conditions.

  6. Countries with more democratic governments have more sustainable energy policies.
    Extended Data Fig. 2: Countries with more democratic governments have more sustainable energy policies.

    Energy sustainability index (as measured by the World Energy organization) is shown as a function of the democracy index (as measured by The Economist Intelligence Unit) for n = 128 countries. A strong positive association is clearly visible, and this association is robust to controlling for gross domestic product (GDP), Gini index, population size, literacy rate, unemployment rate, life expectancy and level of corruption. Thus we provide preliminary empirical support for the role of democracy in promoting sustainability outside the laboratory. We adopt the colouring and naming scheme from The Economist Intelligence Unit’s classification of regimes.

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Author information

  1. These authors contributed equally to this work.

    • Oliver P. Hauser &
    • David G. Rand

Affiliations

  1. Program for Evolutionary Dynamics, Harvard University, Cambridge, Massachusetts 02138, USA

    • Oliver P. Hauser,
    • Alexander Peysakhovich &
    • Martin A. Nowak
  2. Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts 02138, USA

    • Oliver P. Hauser &
    • Martin A. Nowak
  3. Department of Psychology, Yale University, New Haven, Connecticut 06511, USA

    • David G. Rand &
    • Alexander Peysakhovich
  4. Department of Economics, Yale University, New Haven, Connecticut 06511, USA

    • David G. Rand
  5. Department of Mathematics, Harvard University, Cambridge, Massachusetts 02138, USA

    • Martin A. Nowak

Contributions

O.P.H., D.G.R., A.P. and M.A.N. designed and performed the experiments, analysed the data and wrote the paper.

Competing financial interests

The authors declare no competing financial interests.

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Author details

Extended data figures and tables

Extended Data Figures

  1. Extended Data Figure 1: Bootstrapping simulations demonstrate the robustness of full voting and the failure of partial voting. (275 KB)

    We address sources of noise in the sequence of events that occurred in our experiment by conducting a set of computer simulations using the data generated by our participants. We randomly sample (with replacement) a series of generations of participant decisions, and calculate the fraction of those generations in which the pool was refilled. For each condition, we simulate 10,000 pools (or 1,000,000 pools if δ < 0.8) for 15 generations. a, Simulated data for the unregulated, full voting and partial voting conditions show that full voting is by far the most successful at sustaining the pool. b, Simulated data for the T = 40%, T = 30%, δ = 0.7 and δ = 0.6 conditions shows that reducing δ has only a small effect, and although reducing T does undermine sustainability, the effect is much less striking than that of unregulated or partial voting despite the higher value of T in these less-regulated conditions.

  2. Extended Data Figure 2: Countries with more democratic governments have more sustainable energy policies. (182 KB)

    Energy sustainability index (as measured by the World Energy organization) is shown as a function of the democracy index (as measured by The Economist Intelligence Unit) for n = 128 countries. A strong positive association is clearly visible, and this association is robust to controlling for gross domestic product (GDP), Gini index, population size, literacy rate, unemployment rate, life expectancy and level of corruption. Thus we provide preliminary empirical support for the role of democracy in promoting sustainability outside the laboratory. We adopt the colouring and naming scheme from The Economist Intelligence Unit’s classification of regimes.

Supplementary information

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  1. Supplementary Information (2.7 MB)

    This file contains Supplementary Text and Data, which includes Supplementary Methods, Supplementary Tables 1-7 and additional references.

Additional data