Summary: Study identifies distinct neural processes that occur when we make decisions for the benefit of ourselves and of others.
Is a selfish person just processing the decisions that result in rewards to others differently? Perhaps, suggests a recent RIKEN study. A RIKEN team, led by Hiroyuki Nakahara of the Laboratory for Integrated Theoretical Neuroscience at the RIKEN Center for Brain Science, discovered this when they examined 36 healthy volunteers aged between 20 and 32 years. Their aim was to find out which parts of the brain are activated when considering giving rewards to others.
These volunteers were asked to choose one of two options, each with a baseline reward to themselves. One option then involved an extra financial reward for the participants and the other, a reward to ‘others’—in this case a series of well-known charities.
The group looked at what happened when a person is giving an extra reward to one of the charities, using functional magnetic resonance imaging (fMRI) and a computational modeling method called a connectivity analysis. They discovered that there is a three-stage cascade process involved.
In the first stage, the brain detects a perceived benefit to others. The first stage was accompanied by neural activity in the right temporoparietal junction (right TPJ) and the left dorsolateral prefrontal cortex (left dlPFC)—regions that are well known to play a role in attention and social interaction.
The second stage involves understanding the impact of the offer of value on the outcome. This corresponded to activity in the right anterior insula (right AI), a key node of a brain circuit called the salience network, which has been associated with empathy.
The third stage is the actual decision-making process. Decision-making corresponded to activity in the medial prefrontal cortex (mPFC), supporting findings from previous studies that have implicated the mPFC in strategic reasoning.
Next, the team explored whether there might be any common patterns in the neural pathways involved in the choice to give to others in individuals who can broadly be described as either generous or selfish. For this, the team used a test established by social psychologist Paul A. M. Van Lange of Vrije Universiteit Amsterdam in the 1990s. The test enables scientists to gauge a person’s preference regarding the allocation of rewards to themselves and others. This social value orientation (SVO) test is widely used in social
psychology and other disciplines, such as economics.
The volunteers took the SVO test in the form of a questionnaire and were subsequently classified as either prosocial (i.e. having a tendency towards generous behavior) or individualistic (having a tendency towards selfish behavior).
One of the most striking findings was that there was a distinct difference in the neural processes involved in giving to others between prosocial and individualistic subjects. This difference existed even when the two groups chose similar things in the original task.
Nakahara considered it particularly intriguing that prosocial subjects used a similar brain process for other-bonus and self-bonus choices, mediated via the left dlPFC–mPFC pathway. Individualist subjects, on the other hand, mediated the process of weighing up giving to others in a different way to the self-reward choice. In the second stage of the process, more ‘selfish’ subjects mediated the choice to give to others by the right AI, which represents where the brain may digest the implications of the benefit-to-others option.
This isn’t all about selfishness and generosity, but rather perceptions of value, emphasize the researchers. Rather than being altruistic, a generous subject may be perceived more value in social contributions or be subject to predispositions such as inequity aversion and guilt. The team have called the process of deciding to give to others ‘social value conversion’. In the paper, the team predicted that social value conversion is actually a primitive computation that may be essential for different forms of social behavior.
The team’s findings provide building blocks for investigating more complex forms of social decision-making. Exploring ideas about generosity and selfishness would call into question the role of cultural and religious factors, and variations across countries and regions, for example, in accounting for how we each perceive and take on board consideration
These multifarious factors “would certainly contribute to shape more complex types of social behaviors,” Nakahara explains. “Through repeated experiences in daily life, they would be built-in as part of the neural circuitry of social behavior and decision-making. The building blocks of the social conversion process would then be modulated and integrated with those processes to produce a final behavior and decision.”
Another promising research direction, albeit one that goes beyond the scope of the present study, would be to look at the possibility that the process involved in giving to others might in some way be different in people with antisocial disorders. Such differences, if identified, may contribute to understanding of the neural correlates of antisocial behavior.
Nakahara’s team is continuing to work on uncovering further insights into of social decision-making. “One of our ongoing studies investigates how people seek to make better decisions by predicting the decisions of others, and we are getting some interesting results,” he says.
Hiroyuki Nakahara – RIKEN
The image is credited to Sebastian Kaulitzki.
Original Research: Closedn access
“Computing Social Value Conversion in the Human Brain”. Haruaki Fukuda, Ning Ma, Shinsuke Suzuki, Norihiro Harasawa, Kenichi Ueno, Justin L. Gardner, Noritaka Ichinohe, Masahiko Haruno, Kang Cheng and Hiroyuki Nakahara.
Journal of Neuroscience doi:10.1523/JNEUROSCI.3117-18.2019.
Computing Social Value Conversion in the Human Brain
Social signals play powerful roles in shaping self-oriented reward valuation and decision making. These signals activate social and valuation/decision areas, but the core computation for their integration into the self-oriented decision machinery remains unclear. Here, we study how a fundamental social signal, social value (others’ reward value), is converted into self-oriented decision making in the human brain. Using behavioral analysis, modeling, and neuroimaging, we show three-stage processing of social value conversion from the offer to the effective value and then to the final decision value. First, a value of others’ bonus on offer, called offered value, was encoded uniquely in the right temporoparietal junction (rTPJ) and also in the left dorsolateral prefrontal cortex (ldlPFC), which is commonly activated by offered self-bonus value. The effective value, an intermediate value representing the effective influence of the offer on the decision, was represented in the right anterior insula (rAI), and the final decision value was encoded in the medial prefrontal cortex (mPFC). Second, using psychophysiological interaction and dynamic causal modeling analyses, we demonstrated three-stage feedforward processing from the rTPJ and ldPFC to the rAI and then from rAI to the mPFC. Further, we showed that these characteristics of social conversion underlie distinct sociobehavioral phenotypes. We demonstrate that the variability in the conversion underlies the difference between prosocial and selfish subjects, as seen from the differential strength of the rAI and ldlPFC coupling to the mPFC responses, respectively. Together, these findings identified fundamental neural computation processes for social value conversion underlying complex social decision making behaviors.
In daily life, we make decisions based on self-interest, but also in consideration for others’ status. These social influences modulate valuation and decision signals in the brain, suggesting a fundamental process called value conversion that translates social information into self-referenced decisions. However, little is known about the conversion process and its underlying brain mechanisms. We investigated value conversion using human fMRI with computational modeling and found three essential stages in a progressive brain circuit from social to empathic and decision areas. Interestingly, the brain mechanism of conversion differed between prosocial and individualistic subjects. These findings reveal how the brain processes and merges social information into the elemental flow of self-interested decision making.