Failures of cognitive control are common. Why do we so often fail to exert cognitive control? Classic (prefrontal) models of cognitive control address our ability to implement control. Recent advances have shifted the question to how we decide whether to recruit cognitive control. This involves re-conceptualizing cognitive control as a cost/benefit-based decision instead of an ability of implementation. I will review evidence that dopaminergic drugs like methylphenidate alter cognitive control, not just by modulating the ability to implement cognitive control, but also by biasing cost/benefit decision making about whether or not to exert cognitive control.