Trust is part of your brain’s default setting, but the feeling may not be as noble as your teachers made it out to be. Neuroscience has an explanation that relies on a lot of fascinating biochemistry.

In one study, scientists asked 49 participants to play a two-person game of trust. One participant had to act as a broker while the other worked as a trustee. Working together, the two built up a pot of money by investing in each other. But to amp up the risk—and the trust—there was one major caveat: One of the participants could steal all of the money at any moment.

Before playing the game, some of the participants snorted a nasal spray laced with oxytocin. Best known for being the “love hormone,” the scientists suspected that oxytocin also had a hand in making us trustworthy. It seems they were right. Participants who sniffed the oxytocin spray ended up investing more money than those who had inhaled a placebo. It seems the burst of oxytocin had increased their trust.

But the takeaway isn’t so warm and fuzzy. As participants trusted each other more and more, a brain area called the caudate nucleus—one of the brain’s pleasure centers—lit up. As their trust solidified, the caudate became active earlier and earlier. That is, they started taking the benefits for each investment for granted. The researchers concluded that we don’t trust people because it’s some universal moral force. We trust people because it rewards one of the brain’s pleasure-seeking centers. Our brain simply likes getting that oxytocin-laced caudate kick.  

Trust us. You'll want to tune in to Brain Games Mondays at 9/8c on the National Geographic Channel to discover all the astonishing things your brain can do.