Our generosity may be motivated in two ways: we can give out of empathy (to someone who has deeply touched us, for example) or out of reciprocity (to someone who has done us a favor). A team of psychologists and neuroscientists led by Grit Hein and Ernst Fehr at the University of Zurich has managed to distinguish these two types of motivation for giving by using brain imaging. How are compassion and gratitude seen in the brain?

In psychology, motivation is considered to be independent from human behavior. These mental constructions cannot be directly observed. As a result, they are generally deduced from individual behavior. But different motives can lead to an identical behavior. The researchers wondered if it were possible to obtain a distinct neurophysiological representation for each motive and thus predict the motivation behind each behavior. The scientists chose altruistic human decision-making as the context for exploring two specific motivations: empathy and reciprocity.

To do so, the researchers placed participants in situations where they could make either selfish or altruistic choices. For the latter in particular, the scientists studied the two types cited earlier: compassionate altruism and reciprocal altruism. The participants were randomly assigned to one of the two groups. In each situation, the participants were paired with a partner. In the first group, the subject saw his or her partner receive electrical shocks and could pay to prevent their partner from further suffering. In the second group, each participant was first placed in the victim role, with the partner paying to prevent the participant from receiving the shocks. In the first situation, the giving was out of sheer compassion, while in the second group, the giving was reciprocal: you helped someone because they helped you.

What did the authors of this study published in Science observe? The fMRI images revealed that participants showed activity in three brain areas: the anterior cingulate cortex, anterior insula. and ventral striatum. But the patterns varied according to the situation. Indeed, during altruistic compassion, the anterior cingulate cortex activates the insula which blocks the ventral striatum, while in reciprocal compassion, the anterior cingulate cortex is also activated in turn by the insula, and the insula activates the striatum. Thus, using brain imaging, it's easy for neuroscientists to tell to which experimental situation participants belong.

Moreover, in selfish people, the empathy situation (but not reciprocity) increased the number of altruistic decisions. The opposite was true for altruistic participants. Thus, relatively selfish individuals can become more generous if their empathy is solicited, while “natural” altruists are less receptive to this type of influence (as they are already quite empathetic), but are more likely to be influenced by reciprocity.

In this end, this study emphasizes the existence of different brain networks, each activated by a particular motivation for giving. It also demonstrates that our altruistic behaviors can change (improve) according to the situations in which we find ourselves.