Cognitive control has been defined in various ways, but includes a reference to the coordination of thoughts or actions with respect to goals or intentions, which presumably subsumes the ability to flexibly adapt behaviour with respect to particular task demands, in order to optimise performance. Evidence for the functional contribution of prefrontal serotonin to cognitive control comes from probabilistic reversal learning and decision‐making paradigms. Human psychopharmacological studies discussed in the context of clusters of experimental paradigms with common neurochemical sensitivities. A compelling, albeit less specific, source of evidence on the role of dopamine (DA) comes from dopaminergic manipulations in patients with Parkinson's disease (PD), in whom neurodegeneration leads to extensive dorsal striatal deficits that progressively encroach on ventral regions and the prefrontal cortex (PFC). Dopaminergic effects are also seen on more complex tasks of rule formation and planning.