The Philosophical Review/Volume 1/Summary: Lipps - Optische Streitfragen
(1) Zu Dr. Otto Schwarz' "Bemerkungen über die von Lipps u. Cornelius besprochene Nachbilderscheinung." If the eye be rapidly turned away from a bright object, a streak of light seems to shoot from the object in the opposite direction. Lipps explained this phenomenon (Bd. I, S. 60 ff.) as due to the underestimation of quick eye-movements. Dr. Schwarz, who attempted a different explanation (Bd. III, Hft. 5) misunderstood or misread parts of the original paper; and the present remarks are mainly directed towards the correction of his article. The question at issue is an important one, and has hardly as yet received a final answer. (2) Zu Franz Brentano's "Ueber ein optisches Paradoxon." The fact of the over- and under- estimation of distance in certain cases of optical illusion was explained by Brentano (Bd. III, Hft. 5) by the over- and under-estimation of large angles. Lipps points out, in an acute paper, that this explanation is not adequate; and that, even if adequate, it would not necessarily exclude the operation of other factors. He himself regards the illusions as dependent on the idea of a free or inhibited movement along the lines bounding the figures. The view is set forth at length in his Aesthetische Faktoren der Raumanschauung (Helmholtz’ Festschrift). Systematic experimentation would seem to be the only method by which certainty can be attained in this vexed chapter of psychological optics.