In the current study, we examined the underlying neural mechanisms that may promote prosocial decisions. Prosocial decisions are often governed by competing rewards between one's own self-interests and the desire to help another. Our study suggests that individuals with prosocial preferences utilize neural processes involved in self-control and mentalizing when making prosocial decisions, and these neural activations may be a precursor to the rewarding nature of giving to others.
Although prosocial behaviors may be inherently rewarding, the decision to help is typically not an automatic process. Individuals must weigh the relative value of helping others with their own self interests and resolve conflict between the two in order to put the needs of another before their own. Behavioral results from our study show that costly decisions take significantly longer to make than personal monetary reward decisions, and costly decisions are related to activation of neural regions involved in self-control. These findings suggest that such prosocial behaviors are not automatic and may involve a degree of personal inhibition in order to resolve conflict between self interests and social motives to ultimately make decisions that help another. In addition to self-control, individuals recruited brain regions involved in mentalizing when making decisions to help their family, suggesting that these decisions also involve shifting attention from one's own self interests to the needs and values of the family.
Researchers have proposed that social preferences shape and govern prosocial behavior (Fehr and Fishbacher 2002
; Fehr and Schmidt 2006
; Caprara and Steca 2007
). The extent to which individuals care about the well being of others has important consequences for their prosocial behavior. In the current study, we measured individuals' family obligation preferences and found that those who placed greater value on the support and respect of their recruited brain regions involved in self-control and mentalizing to a greater extent when making prosocial decisions. These regions were distinct from those found in the main effect of costly-donations versus noncostly-rewards. Thus, individuals with stronger family obligation preferences may be doing something qualitatively different, such as maintaining social rules in memory when they make these decisions. Individuals with lower family obligation preferences showed neural activation around and below zero, suggesting that they were not recruiting brain regions involved in self-control and mentalizing when making prosocial decisions. In fact, activation below 0 suggests that individuals with the lowest family obligation preferences were showing greater neural activation to Noncostly-Reward decisions than Costly-Donations.
Furthermore, individuals who valued helping their family more showed greater functional coupling between the ventral striatum and regions involved in self-control and mentalizing, suggesting, in part, that these neural regions may promote a reward inducing decision for individuals who value helping. Although we propose that the recruitment of brain regions involved in self-control and mentalizing facilitate prosocial behaviors and ultimately enable individuals to gain a sense of reward from helping their family, it is also possible that individuals who value family obligation feel more rewarded from helping and thus recruit more self-control and mentalizing. Finally, we did not find a main effect of ventral striatum activation to Costly-Donation compared to Noncostly-Reward decisions. This is consistent with our previous work, in which we found variability in the extent to which individuals recruited the ventral striatum when making costly contributions to their family (Telzer et al. 2010
), suggesting that ventral striatal recruitment may be modulated by other neural processes during prosocial decisions. Indeed, in the current study, we found ventral striatum activation only in conjunction with neural regions involved in self-control and mentalizing for individuals who value family obligation preferences, suggesting that the extent of ventral striatal activation to prosocial decisions depends upon individual differences and is not a uniform, main effect.
We believe that the capacity to recruit self-control and mentalizing during prosocial decisions depends on individuals' values and prosocial preferences (Caprara and Steca 2007
; Fehr and Fishbacher 2002
), but it is also possible that individuals who recruit these neural processes to a greater extent develop more prosocial preferences over time. Longitudinal research should test this latter possibility. If it is true that prosocial preferences guide neural processing, future research could test whether making prosocial behavior motivationally significant for any individual leads to increased self-control and mentalizing activations. This could have important implications for increasing prosocial behavior in the general population.
Economic research has attempted to understand why and how prosocial behaviors occur. Most previous work has focused on prosocial behaviors towards strangers and charities. Yet, a majority of prosocial behavior occurs on a daily basis between individuals who know each other well, such as one's family. Our study extends the large body of social neuroecomomic research by exploring helping behavior towards the family. We cannot empirically differentiate whether our findings are family-specific or whether we are tapping prosocial behavior toward others more generally. We do not know from our data whether individuals would also use self-control and mentalizing processes when making decisions to help unknown others. If individuals don't know another's needs, goals, or values, they may be less likely to mentalize when making decisions to help them. Furthermore, there may be less at stake if individuals make a decision to help a stranger instead of a close other and thus the conflict between the self and other may be minimized, so they may be less likely to use self-control. Future research should examine whether charitable donations engage regions involved in self-control and mentalizing and whether these regions are related to reward activation.
In summary, prosocial decisions can be complex and difficult to make. Such decisions often involve personal sacrifices that do not incur any direct immediate benefits to the self. Thus, individuals must weigh the relative value of helping others. Our findings suggest that multiple neural processes are involved in these decisions, including mentalizing and self-control. The capacity to utilize these neural processes is shaped, in part, by individual differences in other-regarding preferences, which together may help individuals to make prosocial decisions and ultimately gain a sense of reward.