Neuroeconomic Studies of Impulsivity: Now or Just as Soon as Possible?

Existing behavioral studies of inter-temporal choice suggest that both human and animal choosers are impulsive. One possible explanation for this is that they discount future gains in a hyperbolic or quasi-hyperbolic fasion (Laibson, 1997; Frederick, Loewenstein and O'Donoghue, 2002). This observation stands in contrast to standard normative theory which predicts exponential discounting for any single maximizing agent (Strotz, 1956). This disparity between empirical and normative approaches is typically explained by proposing that human choosers suffer from inner conflict: balancig and impulse for an immediate gratification against other forces calling for delayed gratification (Thaler and Shefrin, 1981; Laibson, 1997; Fudenberg and Levine, 2007; Benhabib and Bisin, 2004; Bernheim and Rangel, 2004; Gul and Pesendorfer, 2001). We hoped to better understand both the behavioral and algorithmic roots of this phenomenon by conducting a series of behavioral and neurobiological experiments on inter-temporal choice. The results of our behavioral experiments deviate significantly from the predictions of both normative and inner conflict models. The results of our neurobiological experiments provide new algorithmic insights into the mechanisms of inter-temporal choice.