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Animals are born with many natural instincts and reflexes. Yet, we as humans possess a unique ability that is “trust”. We have faith in whom we trust, and we place our confidence accordingly. This ability is a key part of being a human, and it is essential to our physical and mental well-being to have someone to trust.

How does this “trust” mechanism work then?

Researchers at Dartmouth University have begun investigating “trust”. In an article in the Journal of Neuroscience, a new study was published that illuminates the science behind this motivation.

 From a biological standpoint, why do we trust?

Image Source: Tom Merton

In the experiment, participants played an economic investment game in which they partnered with a close friend, a stranger, or a slot machine. By monitoring the subjects’ behavior, scientists hoped to better understand collaboration, an activity that relies on an individual’s ability to place trust.

In truth, the friend, stranger, and slot machine were unreal, just simple constructs drawn up by a computer program!

These simulations, set in place by a computer algorithm, reciprocated trust 50% of the time by rewarding players’ helpful actions. From this algorithm, the researchers constructed a computational model that would help predict the players’ decisions based on their previous game experiences.

What motivates decision-making–economic gain or social interaction?

The results were predictable. Participants felt rewarded when they had positive interactions with a close friend rather than with a stranger or slot machine. Correspondingly, the “social value” model that predicted investment decisions based on social values proved more realistic than the model based on financial returns.

 Slot machines were one of the entities with which participants communicated.

Image Source: Matthias Tunger

Researchers studied two brain areas that play a vital role in the decision-making process to explain the findings: the ventral striatum, a brain pathway important for reward processing, and the medial prefrontal cortex, which helps represent others’ mental states. Neuroimaging revealed that the ventral striatum and medial prefrontal cortex correlated with social value signals when the participants made their decisions.

There is more trust associated with a friend’s response than a stranger’s, and a greater social reward signal.  This additional signal aided in decisions that preferred friends, in spite of knowing that each responded 50% of the time.

“These findings show the importance of social relationships in how we make everyday decisions, and specifically how relationships can change our perceived value associated with a given decision,” says co-author Chang, an assistant professor in Psychological and Brain Sciences at Dartmouth.

Feature Image Source: Christian Scheja

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