Another example of the difference between subjective space and physical space is the Kundt-Münsterberg illusion. In this illusion, the temporal half of a horizontal line, when viewed monocularly and kept at right angles to the line of sight at the point of bisection, will appear shorter than the nasal half of that bisected line. Because of this illusion, when an attempt is made with one eye to bisect the horizontal line, the temporal segment will be longer than the nasal. This is the famous partition experiment of Kundt, a German physicist of the mid nineteenth century. The opposite phenomenon, described by Münsterberg, occurs only rarely. Similarly, the lower line segment (imaged retinosuperiorly) is shorter than the upper (retinoinferior) segment. In subjective space, therefore, the equivalent of a true circle fixated centrally is a somewhat irregular round figure, the smallest radius of which points outward. Accordingly, a subjectively true circle does not correspond to a true circle in physical space (Fig. 4.2). In general, the discrepancies in the two eyes are symmetrical. They compensate each other, and the partition of a line into two equal segments is more nearly correct in binocular fixation. The distribution of the subjective retinal spatial values differs between the nasal and temporal halves of the retina.