The Neuroscience behind Trust

You might have noticed your brain ticking and giving you signals when someone is not trustworthy.

I was pleasantly surprised to see its relationship with ventral striatum (which is a part of basal ganglia) of the brain, and stress hormones like cortisol and oxytocin. It's all science, as I expected!

"In the new study, participants thought they were playing an economic investment game with a close friend, a stranger or a slot machine. In reality, they were playing with a simple algorithm that reciprocated trust 50 percent of the time. The researchers developed a computational model that predicted each player’s decision for each round given their previous experiences in the game.

Results showed that participants found positive interactions with a close friend more rewarding than interactions with a stranger or slot machine, and that the researchers’ “social value” model predicted participants’ investment decisions better than models that only considered financial payoffs.

Neuroimaging also showed that specific brain signals — in the ventral striatum and medial prefrontal cortex — correlated with social value signals when the participants made their decisions.

The ventral striatum is a key pathway in reward processing, while the medial prefrontal cortex is associated with representing another person’s mental state. Together, these regions provide additional evidence that players receive a greater social reward signal when they learn their friend reciprocated than the other two players in the game. This occurs despite participants learning that each player is only reciprocating 50 percent of the time. But because players receive this additional reward signal, they end up trusting their friend more than the other players throughout the game."

The image shows: Bilateral activation in the amygdala, left ventral striatum and right dorsal striatum as a function of participants’ investment choices during the delivery of their outcomes. The color map defines the strength of the contrast’s T-scores (Statistical maps with an initial threshold of uncorrected p < 0.001 were established and were subsequently corrected for multiple comparisons using a Family Wise Error corrected cluster threshold of p < 0.05).