Given the chance to vote, people will leave behind a legacy of resources that ensures the survival of the next generation, a series of experiments by Yale and Harvard psychologists show. However, when people are left to their own devices, the next generation isn’t so lucky.

“People want to do the right thing; they just need a little help from their institutions,” said David Rand, assistant professor of psychology at Yale and a co-author of the study appearing June 25 in the journal Nature.

The experiments shed light on the psychology underlying issues such as Social Security funding or resource conservation, in which the interests of future generations are at stake.

The study builds upon “public goods” economics experiments that consistently show that people are willing to forego immediate reward if convinced the group as a whole will benefit. But Rand and Harvard colleagues Martin Nowak, Oliver Hauer, and Alexander Peysakhovich wanted to know if people would be willing to sacrifice resources if the benefit accrues not to individuals in a group, but to people not yet born.

In their experiments, they broke subjects into groups of five and gave them 100 units to spend. In one experiment, each individual could take out up to 20 units, but if the group as a whole used more than 50 units, all successor groups would get nothing. If a given group showed restraint, a line-up of successor groups — new generations each consisting of five new people — would be given the same choices.

The good news was that more than two out of three people were willing to take only 10 units — the sustainable “fair share” allotment — for their own use and preserve resources for the next generation. The bad news was that the minority of selfish individuals consistently destroyed the resource for future generations. Even one or two people in the group taking more than their “fair share” was enough to push the group over the 50 unit threshold, exhausting the resource. In 18 experiments in which individuals were free to extract more than 10 units, only four groups left enough resources to support a second generation, and by the fourth generation, all resources were exhausted.

The results changed dramatically when democratic principles were introduced. All five members of the group voted for a number of units to take. The median vote was then taken out for all group members. In this scenario, all groups passed on enough resources to sustain future generations. Even when researchers made the sacrifice more costly — reducing the “sustainable” level of units available to the group to 40 or even 30 — a majority of groups passed resources down through generations.

Problems arose in a third scenario when only three of five members voted on how many units to take. The results of the vote were not binding for the other two subjects. Here sustainability failed, because a selfish person not bound by the vote could over-consume and destroy the resource.

The latter results would be equivalent to Kyoto protocols, a non-binding attempt to get nations to reduce carbon emissions, the authors noted.

“You are wasting your time if voting results are not binding on everyone,” Rand said.

While voting may be potentially challenging for global-level international agreements, it is much more promising for local- or national-level sustainability policies, note the researchers. In a final analysis of real-world data, Rand and colleagues show that democratic countries of the world have made most advances toward sustainability, even when accounting for factors such as wealth, population size, economic output, and inequality.

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