To investigate the influence of input from fellow group members in a constrained decision-making context, we consider a game in which subjects freely select one of two options (A or B), and are informed of the reward resulting from that choice following each trial. Rewards are computed based on the fraction × of past A choices by two functions fA (x), f B (x) (unknown to the subject) which intersect at a matching point x̄ that does not generally represent globally optimal behavior. Playing individually, subjects typically remain close to the matching point, although some discover the optimum. We investigate the effects of additional feedback regarding the choices and reward scores of other players. We generalize a drift-diffusion model, commonly used to model individual decision making, to incorporate feedback from other players, study the resulting coupled stochastic differential equations, and compare the distributions of choices that they predict with those produced by a pool of subjects playing in groups of five without feedback and with feedback on other players' choices.