 Eye movement measurements are also used to investigate psychiatric disorders.For example, ADHD is characterized by an increase of antisaccade errors and an increase in delays for visually guided saccade.When the brain is led to believe that the saccades it is generating are too large or too small (by an experimental manipulation in which a saccade-target steps backward or forward contingent on the eye movement made to acquire it), saccade amplitude gradually decreases (or increases), an adaptation (also termed gain adaptation) widely seen as a simple form of motor learning, possibly driven by an effort to correct visual error.