Dramatic errors in the perception of motion and depth can result from temporal variations in visual information processing between the eyes. The Pulfrich effect results from processing lags between the eyes, which causes oscillating objects in the frontal plane to be mistakenly viewed as moving along almost circular depth motion trajectories. For a study, researchers sought to explain the anomalous Pulfrich effect, a previously described but poorly understood variety.
When the variation was observed, the illusory motion trajectory appeared aligned with the genuine direction of motion but was orientated left- or right-side back in depth. The findings suggested that the apparent misalignment was caused by interocular differences in brain temporal integration periods rather than interocular disparities in latency. The effective motion amplitude in one eye compared to the other was dampened for oscillating motion due to variations in the period of temporal integration. Different motion amplitudes created the apparent misorientation of the motion trajectories in a dynamic counterpart of the Geometric effect in stereo-surface-orientation perception. Forced-choice psychophysical studies with varying spatial frequencies and onscreen motion damping in the two eyes have found a correlation between reported depth misorientation and the eye with more motion damping.
More concrete proof that interocular variations in temporal integration and delay are what create the anomalous Pulfrich effect was provided by a target-tracking experiment. The results underscored the computational challenges that temporal variances in sensory processing presented to the visual system. Research in the future will examine how the visual system overcomes these obstacles to produce accurate perception.
Reference: jov.arvojournals.org/article.aspx?articleid=2783845
