Interdisciplinary Center for Economic Science (ICES), George Mason University
Working for Others: Theory of Mind in the Absence of an Intentional Agent
(Joint work with Steven Saletta, Frank Kruger, Erte Xiao and Kevin McCabe)
Intentionality detection is frequently identified during interpersonal exchange. Previous studies in this area have focused on strategic interactions between a decision-maker and a counterpart. How a potentially altruistic decision-maker evaluates outcomes accruing to another person who not present during decision making (and who cannot reciprocate) remains an open question. Using fMRI, we implemented a modified dictator game without a punishment option, augmenting or replacing money cost with effort. In a delayed match to sample task, subjects (n=18) earned money for themselves or a known counterpart who was not present during decisions and who had no opportunity to reciprocate or influence payoffs. Comparing outcomes accruing to counterpart versus those accruing to self yielded activation in regions previously identified in mentalizing tasks and two-person interactive games: medial prefrontal, superior temporal, and temporal pole regions. We argue these regions respectively bind shared mental intentions, social identity, and social feature knowledge to predict how outcomes are evaluated by the counterpart. These results shed important new light on the biological foundations of human altruism.
Universitat Pompeu Fabra
Assessing strategic risk with fMRI
(Joint work with Giorgio Coricelli (CNRS Lyon), Andrea Brovelli (CNRS Marseille) and Frank Heinemann (TU-Berlin))
We used fMRI to measure the neural correlates of strategic uncertainty in games and risk in lotteries. Participants played a series of stag hunt games, entry games, and lotteries, all framed in a similar way. The two games differ in their equilibrium properties: stag hunt games are games of strategic complementarity (e.g., an investment pays off if and only if a sufficient number of agents invest in the same industry, so all invest and nobody invest are two Nash equilibria) while entry games are of strategic substitutability (e.g., if too many agents invest in a new market all get nothing; here we should not all do the same, but instead choose mixing strategies in equilibrium). A mentalizing network (mPFC, TPJ, STS, precuneus) is activated in games playing vs. Lotteries, thus distinguishing the social and the private nature of the choice context. Furthermore, we found a behavioral correlation and a similar pattern of activity in the striatum between choosing lotteries and choosing the stag hunt game; while insula and lateral OFC activity was mainly related to entry games choices. Interestingly, we found a clear separation of insula activity in lotteries and stag hunt games when distinguishing between risk averse and risk loving players. However, in entry games this distinction is not at all found. We conclude that the entry game creates more strategic uncertainty as predicted by the nature of the theoretical equilibrium which also involves levels of reasoning. While the strategic uncertainty of the stag hunt game can be “reduced” to standard risk, the uncertainty underlying entry games is higher and analogous to ambiguous choices.
University of Minnesota
Strategic Theory of mind in young children
(Joint work with Melissa Kenig and Itai Sher)
Having a Strategic theory of mind (SToM) is defined as the ability to think about the behavior and the thinking of the others, based on the information you have on the other's incentives and the assumption that the others pursue their interest as you do. SToM is different from ToM because it has to integrate the information on incentives with other information that players have.
Center for Studies in Behavioral Neurobiology, Concordia University
Valuation of opportunity costs by laboratory rats
My research team and I study the neural, behavioral, and computational mechanisms underlying the evaluation, selection, and pursuit of goal objects by laboratory rats. Direct electrical stimulation of particular brain sites produces a powerfully rewarding effect that leads the rats to work hard in order to procure additional stimulation. The rewarding effect arises from an observable volley of nerve impulse propagating along the axons of identifiable neurons. Thus, this preparation provides an entry point for tracing brain reward circuitry and for studying its interaction with modulators of reward, such as abused drugs and hormonal signals that regulate energy balance. Unlike natural rewards, “consumption” of the electrical reward does not lead to satiety or habituation, making it possible to study reward-seeking behavior over long periods of time under stable, highly controlled conditions.