Paradoxical stabilization of relative position in moving frames

Abstract

To capture where things are and what they are doing, the visual system may extract the position and motion of each object relative to its surrounding frame of reference [K. Duncker, Routledge and Kegan Paul, London 161–172 (1929) and G. Johansson, Acta Psychol (Amst.) 7, 25–79 (1950)]. Here we report a particularly powerful example where a paradoxical stabilization is produced by a moving frame. We first take a frame that moves left and right and we flash its right edge before, and its left edge after, the frame’s motion. For all frame displacements tested, the two edges are perceived as stabilized, with the left edge on the left and right edge on the right, separated by the frame’s width as if the frame were not moving. This stabilization is paradoxical because the motion of the frame itself remains visible, albeit much reduced. A second experiment demonstrated that unlike other motion-induced position shifts (e.g., flash lag, flash grab, flash drag, or Fröhlich), the illusory shift here is independent of speed and is set instead by the distance of the frame’s travel. In this experiment, two probes are flashed inside the frame at the same physical location before and after the frame moves. Despite being physically superimposed, the probes are perceived widely separated, again as if they were seen in the frame’s coordinates and the frame were stationary. This paradoxical stabilization suggests a link to visual stability across eye movements where the displacement of the entire visual scene may act as a frame to stabilize the perception of relative locations.

Exploring the Frame Effect

“…We find that both the displacement and the motion generate position offsets, but they act independently. The displacement effect is independent of speed and dependent on the size of the displacement (Özkan et al, 2021); whereas, the effect of pure motion is speed dependent, independent of path length (Cavanagh, MacLeod, & Anstis, 2021). Pure motion is tested here using reverse apparent motion (Anstis, 1970) and the stimulus offers no discernible landmarks to carry displacement information.…”

“…The earlier article (Özkan et al, 2021) already established that the frame’s motion can separate the perceived positions of the flashes by as much as the frame’s travel — equivalent to being seen in frame coordinates (the locations in the frame where the probes were when they flashed) with the frame stationary. In this case, its motion would be completely discounted.…”

“…Previously, the frame effect has been shown to be a remarkably strong illusion, separating aligned flashes by as much as the distance the frame travels (Wong & Mack, 1981; Özkan et al, 2021). Here we explored a wide number of factors to evaluate their influence on the effect.…”

“…However, this earlier literature on frame effects typically examined static (Duncker, 1929) or continuously moving probes (Wallach et al, 1978). In contrast, moving frames give far larger effects for flashed rather than continuous probes (Wong &Mack, 1981; Özkan et al, 2021). The illusory offsets can be as large as the frame’s displacement, as if the flashes were seen in the frame’s coordinates and the frame were not moving.…”

“… Abstract Probes flashed within a moving frame are dramatically displaced (Özkan et al, 2021; Wong &Mack, 1981). The effect is much larger than that seen on static or moving probes (induced motion, Duncker, 1929; Wallach et al, 1978).…”