Trust in a friend is associated with a heightened sense of reward from the interaction. (Source: Wikimedia Commons, Credit: Venpia)
According to a study conducted by Professor Luke Chang at Dartmouth College, people find their interactions with close friends more rewarding than interactions with strangers. This holds true even if their chances of being rewarded by either interaction is the same, implying a role of prior trust in establishing such a bond (1,2).
Collaboration is essential to many aspects of society, be they economics, politics, or relationships. One aspect of collaboration is trust, which can be described as “assuming a mutual risk with a relationship partner to attain an interdependent goal”(1). Such relationships end up being rewarding in some way (1).
There are currently two models to explain how trust arises. One is that continued work together leads to a history of reciprocation, causing an expectation of reciprocation. On the other hand, reciprocation itself may be rewarding as it strengthens the bonds between two partners. The researchers wanted to test which one of these happens to be the case (1).
For the study, participants played an investment game while inside the fMRI scanner. During each trial, they could invest with one of three partners: a close friend whom they had brought to the study, a stranger, or a computer. The participants assessed the social closeness they felt with their friend beforehand and were asked to assess the trustworthiness of each of the other three partners. A picture of the friend and stranger were taken to be presented in the fMRI scanner as stimuli (1).
During each trial, the participant was allowed to either keep or invest a dollar with one of the three partners, whose image was displayed on the screen. If the participants kept the dollar, the trial ended, but if they decided to give it to the partner, then the simulated partner would gain three dollars. Then, the simulated partner could either keep the three dollars or share with the participant. The participant was led to believe that the actual friend or stranger was making the decision to keep or share the three dollars, but in reality the responses for all three partners were preprogrammed to share or keep the money at an equal 50% frequency. Participants were later debriefed about what actually occurred (1).
Looking at just the assessments of closeness and trust, participants felt closer and trusted their friends more than the stranger or computer. The stranger was not deemed significantly more trustworthy than the computer (1).
Despite the 50% rate of reciprocity for all three partners during the trials, participants were consistently more likely to share with their friend than the stranger, who in turn was more likely to be shared with than the computer. Additionally, the participants were faster to share with the friend or stranger than with the computer (1).
The neuroimaging data revealed more activity in the ventral striatum and medial prefrontal cortex when the participants interacted with and when their actions were reciprocated by their friend instead of the stranger or computer. This implies that participants found their interactions with and the reciprocation of their friends most rewarding. Additionally, the level of activity in these areas was correlated with the degree of social closeness the participant felt with their friend (2).
The ventral striatum is part of the reward pathway of the brain, while medial prefrontal cortex is involved in representing the mental state of another person. Interestingly, the reward signal in these areas remained consistent despite the equal 50% reciprocity of all three partners, indicating that prior closeness with the friends led to an increased signal and a continued trust over the other partners (1,2).
Chang believes that this research will enhance understanding of social interactions and networks, and he hopes that social and perceived value will be incorporated in macroeconomic models and policy decisions (1,2).
References:
- S. Fareri, L. J. Chang, M. R. Delgado. Computational Substrates of Social Value in Interpersonal Collaboration. Journal of Neuroscience, 2015; 35 (21): 8170 DOI: 10.1523/JNEUROSCI.4775-14.2015
- Dartmouth College. (2015, August 11). Trust me: Research sheds light on why people trust. ScienceDaily. Retrieved August 25, 2015 from www.sciencedaily.com/releases/2015/08/150811103650.htm