What is for me is not for you: brain correlates of intertemporal choice for self and other

Abstract

People have present-biased preferences: they choose more impatiently when choosing between an immediate reward and a delayed reward, than when choosing between a delayed reward and a more delayed reward. Following McClure et al. [McClure, S.M., Laibson, D.I., Loewenstein, G., Cohen, J.D. (2004). Separate neural systems value immediate and delayed monetary rewards. Science, 306, 503.], we find that areas in the dopaminergic reward system show greater activation when a binary choice set includes both an immediate reward and a delayed reward in contrast to activation measured when the binary choice set contains only delayed rewards. The presence of an immediate reward in the choice set elevates activation of the ventral striatum, pregenual anterior cingulate cortex and anterior medial prefrontal cortex. These dopaminergic reward areas are also responsive to the identity of the recipient of the reward. Even an immediate reward does not activate these dopaminergic regions when the decision is being made for another person. Our results support the hypotheses that participants show less affective engagement (i) when they are making choices for themselves that only involve options in the future or (ii) when they are making choices for someone else. As hypothesized, we also find that behavioral choices reflect more patience when choosing for someone else.

Fig. 1

(A) Choice of sooner option significantly differs for today and delay trials [F(1,27) = 33.62, P < 0.001]. (B) Strong discounters significantly more often chose the sooner reward for SELF than for OTHER [t(13) = −2.34, P = 0.036]. (C) Strong discounters chose the sooner reward in SELF significantly more often than in OTHER only in today trials [t(13) = 3.18, P = 0.007]. (D) Response time is significantly shorter in today trials [F(1,27) = 9.12, P = 0.005). *P < 0.05, **P < 0.01, ***P < 0.001; error bars represent standard errors (SE)].

Fig. 2

(A) Brain regions that were activated by choices containing an immediate option compared to choices with only delayed options in SELF. (B) There were no such activation differences between today and delay trials in OTHER. (C) An interaction contrast of temporal distance (today vs delay trials) and receiver (SELF vs OTHER) showed activation differences within the anterior medial prefrontal cortex (aMPFC), ventral striatum (vStr) and pregenual anterior cingulate cortex (pACC). (For visualization, a threshold of 99% was applied to the probability maps.) (D) Parameter estimates indicate that these activation differences were mainly due to elevated activation in today trials in SELF, whereas in all other conditions activation in these brain areas was similarly low.

Fig. 3

Contrast values and brain regions with activation differences in the interaction contrast (temporal distance × receiver) (A) for strong and (B) moderate discounters. (For visualization, a threshold of 99% was applied to the probability maps.)