Eighteen undergraduates experienced Cormack's tactile illusion of a rotated disk. The subjects were tested on the magnitude of this illusion every 5 seconds while continuing to rotate a disk using the forefinger and thumb of both hands. The subjects were given 6d seconds for adaptation prior to the test under each of the following conditions: adapting both hands (BH), adapting the holding hand (HH), or adapting the rotating hand (RH). A control (C) with no adaptation was also prepared. The effect of adaptation decreased in strength in the order: BH, HH, RH, and C. The difference was significant between each pair of the four conditions. The results indicate that the illusion is produced mainly by holding hand adaptation but that rotating hand adaptation also contributes.

Key wards: tactile perception, Cormack's illusion, duration, adaptation