[An analysis of the factors affecting haptic illusion of a rotated disk (author's transl)]

Three experiments were performed to examine the factors affecting Cormack's haptic illusion that a disk held between the thumb and forefinger of one hand and turned by the fingers of the other hand feels longer in the direction of the turning hand. The illusion magnitunde increased with the disk size and was affected by the size of the comparison figures for judging the illusion magnitude. The illusion magnitude decreased for modified stimulus objects which function as disks only for the turning hand, but illusions in other objects which function as disks only for the holding hand was almost equal to that in the perfect disk. This illusion was concluded to be ascribed to the effect of the holding hand rather than that of the turning hand.