Duration of experienced expansion and contraction of a circle.

The stimulus was a white outline circle which for 60 msec. was projected onto a screen 2 m. from S. The diameter of the circle was 10 cm. and the circle line was approximately 1.5 mm. wide. Fixating the center of the circle Ss reported experiencing the circle as expanding from the point of fixation to full size and then contracting to the point of fixation. Ss' experiences fell in two classes. The durations of Ss' experience of expansion-contraction were measured in msec. Ss also participated in experiments in which they fixated the nethermost point of a 17-cm. vertical straight line which was 2 mm. wide. Ss experienced the line as lengthening from the point of fixation to full length and then shortening to the point of fixation. For a given S the duration of the experienced expansion-contraction of the circle and the experienced lengthening shortening of the straight line were the same.