Figure 4.

(a) Changes in the exploration parameter, in units of milliseconds per unit standard deviation of the belief distributions, on tolcapone vs placebo, segregated by genotype (mean±SEM; N_Met/Met=16, N_Met/Val=27, N_Val/Val=21). There is a significant drug x genotype interaction (F(2,61)=3.68, p=0.03) that is driven by a significant differential increase in exploration for the Met/Met subjects relative to the Val/Val subjects. (b) When a median split is performed on locus of control (LOC) scores, the value of the exploration parameter is significantly larger in those with an internal, as opposed to external, LOC (mean±SEM; N_External=37, N_Internal=29). Additionally, in subjects with an external LOC, exploration increased significantly on tolcapone; and this increase was significantly greater than that in subjects with an internal LOC. (*p<0.05).