Average adaptive responses by group.

An adaptive “shift-up” (left) and “shift-down” (right) perturbation was applied to the fo of auditory feedback with a maximum perturbation of 100 cents or -100 cents respectively (schematized in upper panel). Mean adaptive responses in cents are plotted as the mean across five-trial blocks for control speakers (dark blue line) and speakers with Parkinson’s disease (light pink line) with shading indicating 95% confidence intervals.