Public Release: 

Neural connectivity dictates altruistic behavior

American Association for the Advancement of Science

A new study suggests that the specific alignment of neural networks in the brain dictates whether a person's altruism was motivated by selfish or altruistic behavior. In psychology, motives are considered to be drivers of human behavior but can be difficult to discern; simply observing a person's actions is not sufficient to do so. A person may behave altruistically, for example, because they are moved by someone's sufferings (empathy), or they may behave altruistically because they feel obliged to return a favor (reciprocity). Some researchers have suggested that identifying neural networks in the brain associated with certain motives could provide an intriguing window into why a person behaves a certain way. Therefore, Grit Hein and colleagues sought to identify structural differences in the brains of people under two different motive scenarios. They designed an experiment where a participant interacted with two partners. In one experimental group, a participant observed a partner receiving painful shocks, thereby eliciting an empathic response in the participant (empathy group). In the other group, a participant observed partner sacrificing money to save the participant from receiving a shock, thereby eliciting a desire in the participant to return the kind behavior (reciprocity group). In both groups, the participant was also paired with a second partner who served as a control and did nothing for them. Following this part of the experiment, all participants conducted a money allocation task. As expected, participants sacrificed more money to the empathy or reciprocity partner than to the control partner. Critically, the altruism did not differ between the groups, so that the hidden motive of the participant could not be accurately inferred from behavior alone. The researchers studied the participants' brain structures, however, finding distinct patterns. Using a classification algorithm, individual patterns of brain connectivity could be used to detect the specific motive - empathy or reciprocity - for altruism. For example, empathy-driven altruism showed slightly negative connectivity between the anterior insula (AI) and ventral striatum (VS), while reciprocity-driven altruism showed strong positive connectivity between these regions. The volunteers were then partitioned into two groups depending on their level of altruism. "Selfish" individuals could be characterized by low or negative connectivity between the anterior cingulate cortex and AI, whereas predominantly prosocial individuals displayed positive connectivity between these regions. Inducing empathy-driven altruism in the selfish group resulted in connectivity more similar to the prosocial individuals. A Perspective by Sebastian Gluth and Laura Fontanesi provides more context.

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