The activity of midbrain dopamine neurons & mesolimbic dopamine levels are consistently modulated by anticipated future reward more strongly & consistently than effort, even after weighting reward & effort on behavior equally

What Is the Relationship between Dopamine and Effort? Mark E.Walton and Sebastien Bouret. Trends in Neurosciences, https://doi.org/10.1016/j.tins.2018.10.001

Highlights
* Compared to reward, effort remains poorly understood, both at the behavioral and neurophysiological levels.
* Dopamine has been proposed as central to effort-related decision making, but its role is not clearly defined.
* In fact, the activity of midbrain dopamine neurons and mesolimbic dopamine levels are consistently modulated by anticipated future reward more strongly and consistently than effort, even when the weight of reward and effort on behavior are equated.
* These signals may promote decisions to act based on the potential gain from a future reward.

Abstract: The trade-off between reward and effort is at the heart of most behavioral theories, from ecology to economics. Compared to reward, however, effort remains poorly understood, both at the behavioral and neurophysiological levels. This is important because unwillingness to overcome effort to gain reward is a common feature of many neuropsychiatric and neurological disorders. A recent surge in interest in the neurobiological basis of effort has led to seemingly conflicting results regarding the role of dopamine. We argue here that, upon closer examination, there is actually striking consensus across studies: dopamine primarily codes for future reward but is less sensitive to anticipated effort cost. This strong association between dopamine and the incentive effects of rewards places dopamine in a key position to promote reward-directed action.