Trustworthiness has always been a revered personality trait. So much so that most of us are willing to look past any number of distasteful attributes if somebody proves to be 'trustworthy.' Ask the next person you see what they're looking for in a partner, plumber, or political candidate and they're guaranteed to put trust near the top of the list.
Trust is an emotion that's difficult for most people to define; like love. People just know when they feel it. No doubt, most of us would include words like 'truthful,' 'ethical, and 'dependable' in our definitions of what it means to be trustworthy. Such words, though, are themselves abstractions that don't define what it means to trust another person.
How is it, then, that we know when we can trust somebody? What do people do that earns them the distinction of being trustworthy? Why is it that some people are awash with trust, and others reserve the emotion for only a few, select people? And what is it about trust that makes it such an exalted trait?
Like so many other neuropsychological questions, the answers appear to lie within our good friend, dopamine: the ever-present, ever-pervasive, and always welcomed neurotransmitter that provides its host with a strong sense of reward and pleasure. It's the magic brain-gravy that's responsible for things like our desire to eat high-calorie foods and our motivation to perform self-benefiting tasks. According to some recent research, though, dopamine may also be responsible for the establishment of trust between two people.
A team of neuroscientists, Brooks King-Casas and Read Montague, et. al., designed an experiment that centered on a simple economic game in which receiving a reward required participants to trust one another with their money. If a player was feeling a bit greedy, he or she could steal from the pot at any time and, in doing so, erase the trust that had been established. By using a technique called 'hyper-scanning,' researchers were able to monitor subjects' brains as they interacted with other subjects in separate fMRI scanners. It wasn't long before the scientists were able to predict whether or not a player would steal from the pot several seconds before the theft actually took place. The secret to the researchers' clairvoyance was found in imaging of the caudate nucleus during gameplay.
The c-shaped caudate nuclei - found in both of the brain's hemispheres - play key roles in memory formation and the processing of external feedback. They are also heavily innervated by dopamine neurons. As each player participated in the game, it was the caudate nuclei that monitored the actions of the other players.
Initially, the caudate didn't activate until the subjects actually trusted one-another. It was then that each player received their dopamine reward and the caudate nuclei came alive. However, the caudate began to expect those rewards and started firing long before the player received any money from the other participants. The bonds of trust would then strengthen every time the player received their money; reassuring them that they weren't going to be let down.
These findings suggest that trust may not be such a noble trait after all. It appears that the highly regarded emotion may be little more than a gluttonous system designed to satisfy our primitive dopaminergic needs. When I say that someone is trustworthy, I'm really saying that they reliably satisfy some need I have. If you show that you are willing to satisfy that need - thereby flooding all the right parts of my brain with happy juice - I will trust you. And trust me, it feels good.
Main Article: http://www.hnl.bcm.tmc.edu/articles/Read/Getting_TO_Know_You2005.pdf