Trust is its own
reward
Who do you trust? The question may seem distinctly human—and
limited only to “quality” humans, at that—but new research
suggests that trust is handled by the human brain in much the same way
that obtaining a food reward is handled by the brain of an insect. And
it turns out that we can actually trust each other a fair amount of the
time without getting betrayed, just because we are biological creatures.
Experimenters at Caltech and the Baylor College of Medicine
used a new brain-imaging technique called “hyperscanning”
to simultaneously scan the brains of test subjects as they influenced
each other and built trusting relationships in the course of playing an
economic game.
Reporting in the cover story of the April 1 issue of Science,
the researchers described the results they obtained by hooking up volunteers
to functional magnetic resonance imaging (fMRI) machines in Pasadena and
Houston. One volunteer in one locale interacted with another volunteer
he or she did not know, as the two played an economic game in which trustworthiness
had to be balanced with the profit motive. During the game, the brain
activity of the volunteers was continually monitored to see what was going
on.
According to associate professor of philosophy Steve Quartz,
director of the Social Cognitive Neuroscience Laboratory at Caltech, the
results show that trust tended to occur earlier as the game progressed.
That is, trust was delayed in the early rounds of the game; test subjects
then began to determine the costs and benefits of the interchange, and
eventually they anticipated rewards before they were even bestowed, their
neuronal activity demonstrating an “intention to trust” before
the round was finished. Once players knew each other by reputation, their
intentions to trust were revealed about 14 seconds sooner than in the
early rounds of the game.
In other words, the expectation of a reward is intimately
involved in an individual’s assessment of trustworthiness in the
other individual, and the recipient tends to become more trusting prior
to the reward coming—provided that there is no backstabbing.
Colin Camerer, Caltech’s Axline Professor of Business
Economics and the other Caltech faculty author of the paper, wittily notes
that the study is also a breakthrough in showing that game theory continues
to reward researchers who study human behavior.
“The theory about games such as the one we used
in this study is developed around mathematics,” he says. “But
a mathematical model of self-interest can be overly simplified. These
results show that game theory can draw together the social and biological
sciences for new and deeper understandings of human behavior.”
The results of the research interest Camerer and Quartz
on several levels. For one, they demonstrate the neuroscience of economic
behavior. “Neoclassical economics starts with the assumption that
rational self-interest is the motivator of all our economic behavior,”
says Quartz. “The further assumption is that you can only get trust
if you penalize people for non-cooperation, but these results show that
you can build trust through social interaction.”
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