Abstract
The magnitude of the Zöllner illusion was measured for a range of intersect angles in the four combinations of subject, vertical or tilted, and display, horizontal or tilted. When the main lines of the display fall on the horizontal retinal meridian, body tilt per se has no effect; there are however, anomalous results when the body is tilted and the main lines do not fall on the horizontal meridian, and the possible implications are discussed.