Perceptual Additions with Four 90° Arcs as Stimuli

Abstract

The stimulus, 4 black 90° arcs of concentric circles, was viewed under the following three sets of conditions: (a) stroboscopic lighting of 10.5 cps with an increasing number of flashes from 1 to 95, (b) continuous stroboscopic lighting of 10.5 cps, and (c) constant lighting. Ss reported different kinds of experience apart from the perception of the 4 arcs of 90°. These include forms, mainly elongations of the 4 arcs, and additions between the 4 arcs, plus radii, the three forms of which were perceived both in stroboscopic lighting and in constant lighting. Elongations and arc additions become longer and longer with increasing numbers of stroboscopic flashes, and at a certain number of flashes they often grow into circles of 360°. When the number of stroboscopic flashes is increased Ss usually observe an increasing number of radii which, for instance, around 15 flashes reach maximum number of about 16. Elongations and arc additions of 360° and a great number of radii often appear under continued stroboscopic lighting. This new perceptual situation elicits characteristic results from each S, but most Ss form groups with particular characteristics.