Why does it feel effortful to be precise?

Our eye movements are controlled by a relatively simple circuit in the brainstem. Remarkably, it seems to operate with less error when we are motivated by money. We showed that internal feedback gain — a process that stabilises motor plans as they are executed — increases with reward, thus improving the precision of the movement. We propose that feedback signals required for precision are costly for the brain — in our recent paper in Neuropsychologia with Kinan Muhammed and Masud Husain.