trust & reputation building

researchers have found – if simultaneous fMRI scans are to be believed – the “trust” center of the brain:

With the development of trusting feelings, increased blood flow occurred in the caudate nucleus, an area in the rear portion of the brain that is involved in processing rewards. Over time, this increased blood flow appeared earlier as an expectation of trustworthiness was established.

the study was pretty cool. two participants were wired for fMRI and began a trading game that's pretty standard in experimental economics. the “investor” could give her partner money, which would then triple. the partner could then give some of that money back, a method that would create trust in the investor to continue to send money.

with the recognition that social interactions are rarely single-shot, and that trust cannot develop without prior experience, 10 rounds were played. at first, the caudate nucleus lit up when participants knew how much the other was giving them. towards the end - after seven or eight rounds - its neurons began popping even before participants knew whether or not their partner was giving them money at all, indicating that participants are building a model of the investor's next move. that was indeed the case, an additional experiment revealed, when the partner was able to guess more and more accurately what the investor would do over time. this is, essentially, the neuroscience of reputation building.

the caudate nucleus, whose disorder is implicated in such disorders as ADHD, obsessive-compulsive disorder, schizophrenia, parkinson's, and huntington's disease, is part of the striatum, which is one of the basal ganglia, situated kind of in the middle of the brain between the two hemispheres. in this experiment researchers concluded that it handles information regarding the "fairness" of the investor's decision as well as the decision to repay that fairness with trust.

reference: getting to know you: reputation and trust in a two-person economic exchange
brooks king-casas, damon tomlin, cedric anen, colin f. camerer, steven r. quartz, and p. read montague science 1 april 2005; 308: 78-83 [DOI:10.1126/science.1108062]

Labels: decision making, neuroscience