In the 19th century, Bell (1823), Purkyně (1825), and Hering (1861 [1990]), Helmholtz (2005 [1924]), and Mach (1897 [1886]) deployed the efference copy theory to illuminate a variety of experimental findings, e.g., the tendency in subjects with partially paralyzed eye muscles to perceive movement of the visual scene when attempting to execute a saccade (for a review, see Bridgeman 2010.) The theory’s most influential formulation, however, came from Erich von Holst and Horst Mittelstädt in the early 1950s. According to what they dubbed the “reafference principle” (von Holst &amp; Mittelstädt 1950; von Holst 1954), the visual system exploits a copy of motor directives to the eye in order to distinguish between exafferent visual stimulation, caused by changes in the world, and reafferent visual stimulation, caused by changes in the direction of gaze: