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How trustworthy are people? How far do we trust one another?

That’s what researchers set out to discover. In a recently published study, scientists from a number of universities in Spain analyzed the responses of 541 subjects to a variety of social dilemmas. Individuals were grouped into pairs and prompted to make decisions that led to collaboration or conflict.

Studies like this are nothing new. If you’re familiar with the study of human behavior, you’ll recognize this work’s connection with game theory. In his book, Game Theory: Analysis of Conflict, American economist Roger Myerson defined game theory as “the study of mathematical models of conflict and cooperation between intelligent, rational decision-makers.”

In other words, game theory is a way of analyzing the behavior of people when they face a dilemma, and the resulting decisions they make.

But what makes this series of experiments interesting is what the researchers did next: They developed an algorithm to help classify these individuals into specific groups, to see what they could learn from an outside perspective.

How It Works

One popular model that’s used in game theory is known as the prisoner’s dilemma, which goes something like this:

Two gang members are arrested and put in solitary confinement, without the means to communicate with each other. There’s not enough evidence to convict the pair, so prosecutors offer each prisoner a deal: He can betray his partner by testifying against him, or cooperate by remaining silent.

The offer is:

  • If both criminals betray each other, they each serve two years in prison.
  • If A betrays B but B remains silent, A is free to go but B must serve three years in prison (or vice versa).
  • If both criminals remain silent, they go free.

Many variations of the prisoner’s dilemma are played out every day in real life, and the results aren’t so easy to predict.

In this series of experiments, the situations varied in complexity. “Those involved are asked to participate in pairs. These pairs change, not only in each round, but also each time the game changes,” explained one of the authors of the study, Anxo S├ínchez (via Science Daily).

“So the best option could be to cooperate or, on the other hand, to oppose or betray … In this way, we can obtain information about what people do in very different social situations,” said Sanchez.

And here’s where it gets good: Using the algorithm they developed, the researchers organized 90 percent of the subjects into four groups:

Optimistic: This group works on the assumption that they and their partner will make the choice that’s best for all.

Pessimistic: These people generally expect the worst from their partner and tend to select the option that is viewed as the lesser of two evils.

Trusting: This group tends to cooperate out of goodwill, even if doing so provides no benefit to them.

Envious: These individuals don’t care what they achieve, as long as it’s better than the others.

So how many subjects ended up in each group?

You might be surprised to discover that three of the groups–optimistic, pessimistic, and trusting–were roughly made up of the same amount of people, 20 percent.

In contrast, the envious group was the largest, made up of about 30 percent of the participants.

“The really funny thing is that the classification was made by a computer algorithm that could have obtained a larger number of groups, but which has, in fact, produced an ‘excellent’ rating in four personality types,” explained Yamir Moreno, a professor at the University of Zaragoza (one of the universities that participated in the study).

Additionally, the algorithm classified the remaining 10 percent of the subjects into an “undefined” group, in which it was “unable to classify in relation to a clear type of behavior.”

Parting Thoughts

Unfortunately, the experiment seems to indicate that a lot of people you meet today are selfish and out for themselves.

But you should also know that additional research indicates that the most successful people are those who actually give of themselves, putting others’ interests ahead of their own.

So maybe the question shouldn’t be about to which group you currently belong.

Rather, which group do you want to fall under?

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A version of this article originally appeared on