A functional brain imaging study on the neural correlates of altruism in social decision-making

A functional brain imaging study on the neural correlates of altruism in social decision-making Markus Knauff (markus.knauff@psychol.uni-giessen.de) Department of Psychology, University of Giessen Thomas Fangmeier (thomas.fangmeier@uniklinik-freiburg.de) Experimental Neuropsychiatry, University Clinic Freiburg Markus Raabe (markus.raabe@psychologie.uni-regensburg.de) Department of Psychology, University of Regensburg Mark W. Greenlee (mark.greenlee@psychologie.uni-regensburg.de) Department of Psychology, University of Regensburg fMRI study that compared decisions on a set of social prob- lems with non-social problems. In the social problems, the participants were faced with a decision to make an egoistic choice (which would lead to their own benefit, but to the harm of another person) or an altruistic choice (which de- nies their own benefit but would be in the interest of the other person). In the non-social problems, the participants were requested to make choices in which no other person was involved. The social problems resembled the Prisoner's Dilemma game, which is the most widely used paradigm in behavioral sciences to study the roots of cooperation and conflicts between individuals and social groups (Axelrod, 1984). In a Prisoner's Dilemma, an individual can choose between two strategies, either to cooperate with another person or to defect . Each person gains when both cooper- ate. If only one of them cooperates, the defector gains more. If both defect, both gain very little but not as much as the cheated cooperator whose cooperation is not reciprocated. Abstract An fMRI study was conducted to explore the neural basis of altruism in social decision-making. The participants were confronted with a non-monetary version of the Prisoner's Di- lemma which is one of the earliest games developed in game theory. They could make a choice between that which would lead to their own benefit, but to the harm of another person, and one which denies one’s own benefit but would be in the interest of the other person. A comparison between these so- cial problems and a set of matched non-social problems (in which no other person was involved) revealed that a complex neural network of cortical and sub-cortical brain areas is in- volved in making altruistic or selfish decisions. The findings indicate that the decision to behave altruistically relies on the interactions between cognitive control processes in prefrontal cortex and emotional control processes in the amygdala. Keywords: social cognition; social neuroscience; altruism; egoism; prisoner’s dilemma Introduction Development of relatively realistic social di- lemmas – A Pilot study The present study is part of recent endeavors to understand the neural correlates of social cognition. The general conjec- ture of this line of research is that humans have developed neural mechanisms for social cognition that produce appro- priate responses in social interaction with other people. As part of this research area, important work on the neural cor- relates of social cognition has been done, for instance, in the fields of social cooperation, moral decision-making, the ability to understand the thoughts and feelings of other peo- ple (an ability usually referred to as “theory of mind”), and the differences in neural activity during social mentalizing in the first-person and from the third-person perspective. For all these research areas many good review articles are available (social cognition in general: Adolphs, 2001, 2003; Amodio & Frith, 2006; moral reasoning: Greene & Haidt, 2002; Moll, Zahn, de Oliveira-Souza, Krueger, & Grafman, 2005; theory of mind: Frith & Frith, 1999; Leslie, Friedman, & German, 2004; first-person vs. third-person perspective in social mentalizing: Vogeley & Fink, 2003). With the present work we want to contribute a new aspect to the field of social cognitive neuroscience. We report an We started with a pilot study to finds a set of relatively realistic social dilemmas. This study was conducted in a class room prior to the brain imaging study. We constructed a pool of 45 narrative episodes which contained social prob- lems and 45 related episodes of analogous topics but ad- dressing non-social problems. Subjects could either respond in an egoistic or in an altruistic manner to the social prob- lems. The social problems described a profound conflict of interest between the protagonist and another person. The participants could either make a choice which will be to their own interests, but at the cost of harm to the other per- son. Or they could sacrifice their own benefit in favor of the other persons’ interest. Here is an example of a social prob- lem: You are on a diving tour with another person. You have an accident under water. The other’s air tank is broken, and you are both jammed in the rocks. The dilemma is that the air of the remaining air tank might be enough for one per- son to survive until help will arrive, but not for both. If you