EXPERIMENTS ON THE AFTERIMAGES OF STIMULUS CHANGE (DVORAK 1870) - A TRANSLATION WITH COMMENTARY

In 1870 Dvorak rejected Helmholtz's eye-movement account of motion aft ereffects (MAEs) on the grounds that it was inconsistent with previous reports of nonuniform rotation in MAEs induced with Plateau spirals. Subsequent observations with spirals that were modified to induce both expanding and contracting MAEs simultaneously, together with the use of stationary negative afterimages during induction and test, were off ered as further counter-examples to the eye-movement hypothesis. Dvora k's conjectures that perception (and misperception) of movement involv es a unitary perceptual dimension of stimulus change also led him to i nvestigate whether aftereffects comparable to MAEs could be induced al ong other stimulus dimensions in vision (luminance gradients), and in audition (gradients of pitch and intensity). It is suggested that Dvor ak's observations, taken as a whole, may be interpreted as an attempt to provide evidence challenging the Helmholtzian traditions underpinni ng eye-movement accounts of MAEs. The nature and outcomes of these obs ervations are provided in a translation of the original work, and are subsequently discussed in relation to some contemporary empirical coun terparts.