Abstract
The pursuit theory of motion parallax (MP) posits that the visual system uses an internal pursuit eye movement signal to disambiguate the relative depth of retinal image motion. Support is found in psychophysical, modeling, and neurophysiological studies. However, a contrary view is that this depth-sign disambiguation is provided solely from vertical perspective information, and not from the pursuit eye movement system (Rogers, 2016). In a partial replication and extension of previous work, the current set of experiments investigated whether vertical perspective is necessary for the disambiguation of depth from MP. In four different conditions, 10 observers indicated the perceived depth phase (2AFC) of computer-generated random-dot MP stimuli. In the first condition, translating stimuli were presented to observers on a flat CRT monitor providing both vertical perspective and pursuit eye movement cues. Subsequent conditions were designed to eliminate perspective cues, while still eliciting pursuit eye movements. In the second condition, the stimuli were projected on the face of a hemi-spherical Elumens Visionstation, with observer's eye positioned at the radius point. In the third condition, the stimuli were presented on an LCD display that mechanically translated in a single +/- 6 deg arc around the observer's eye position. In the fourth condition, stimuli were presented on an LCD display that mechanically oscillated in a +/- 6 deg arc for a 55 second presentation duration while observers indicated perceived depth phase. In all conditions observers reliably reported perceived depth phase consistent with that predicted by the pursuit theory of MP, despite the absence of vertical perspective cues. Previous work has shown changes in vertical perspective produced by stimulus translation are ineffective for the disambiguation of depth from motion parallax in the absence of pursuit eye movements. Therefore, we conclude that vertical perspective cues are unnecessary for the disambiguation of depth from MP.
Meeting abstract presented at VSS 2018