[Analysis of temporal factor affecting hepatic illusion of a rotated disk]

Twenty-four subjects experienced Cormack's illusion by rotating a disk using fingers of both hands with some pauses inserted during the rotation. Variables were durations for rotating a disk and pause. The illusion magnitude was measured just before each pause. The first experiment showed that the illusion magnitude decreased with increasing the pause. The second experiment showed that there was no difference in illusion magnitude between 5- and 20-second conditions of pause for 20-second rotating duration, although the magnitude was smaller for 20-second pause than that for 5-second pause under the condition of 5-second rotating duration. The experiment also showed that the final magnitude did not depend on whether the magnitude was measured every five seconds or only once at the end of the rotation. The results indicate that pause during rotation contributes to recovering from adaptation due to the rotation and that the effect of pause depends on the duration of rotation. The results also indicate that the increasing illusion magnitude with time is not an artifact due to the method of measuring the magnitude.