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The Science Of Why You Trust Some People More Than Others

Researchers at Dartmouth College have mapped a part of the brain that they say makes you trust friends and strangers differently.
Posted at 12:28 PM, Aug 12, 2015

No trust, no teamwork. Seems obvious, right? Then why has it been so hard to study?

Because trust can take different forms. You can trust someone you don't know well when you take a risk together — like skydiving with an expert whose life is hooked to yours.

But on the flip side, your trust for a friend can outweigh facts and cloud your judgment.

Researchers at Dartmouth College have discovered why your brain makes the trust you feel for friends and strangers unequal and how relationships affect the decisions you make.  

Participants in the study played a game, taking turns working with a friend, a stranger or a computer. One person started with a dollar. They could keep it or invest it in their "partner" and the dollar would become $3. The partner could then keep the $3 or split it 50/50.

The catch? The friend and stranger weren't really playing. The researchers made sure both only split the money with the true participant 50 percent of the time. 

The true participants were hooked up to brain scanners, and researchers found a certain neural pathway gave participants a greater reward signal when they learned their friend acted trustworthy than when the other two players did.

The researchers showed mathematically the true participants made decisions based more on social value than on financial rewards.

One of the researchers said the findings show "how relationships can change our perceived value associated with a given decision."

But the findings go beyond psychology. Economic theories, in particular, have almost exclusively relied on non-personal factors, like financial rewards. 

Possibly the biggest takeaway from this study is the way it maps and quantifies an abstract concept.

And as researchers get better at measuring feelings like trust, we're learning just how much emotions and the need for relationships influence the choices we make.

This video includes images from Getty Images and Katie Tegtmeyer / CC BY 2.0.