An illusion of 3-D motion with the Ternus display

We attempted to eliminate the percept of element motion in the Ternus display by connecting the display elements so that they appeared to be a single object. On each trial, the display elements (two discs) appeared either separated or connected (either via a white line or side by side) and subjects reported whether they observed element motion or group motion at various ISIs. Although it was hypothesized that element motion would be eliminated in the connected condition, subjects observed element motion at short ISIs in the form of a three dimensional illusion in which one element appeared to rotate out in front of (or behind) the other. Implications for short range and long range motion processes are discussed.