The Pulfrich Effect in Virtual Reality

Abstract

The Pulfrich effect, a visual phenomenon where a neural delay in one eye produces a depth misperception, has been directly studied on flat-panel displays but not in virtual reality (VR) environments. Through a series of three experiments, we investigated the relationship between luminance, contrast, dot spacing, and optical blur on the Pulfrich effect in VR and on the perception of motion. In the first two experiments, we found that low-reflectance stimuli produce a stronger Pulfrich effect than high-reflectance stimuli in VR, a result further accentuated by background luminance. Furthermore, the primary experiment showed that nullifying helix rotation motion is a powerful way to study the magnitude of the Pulfrich effect. With data from the first experiment, we developed a compelling VR illusion in which changing the color of a helix reverses the direction of perceived motion. Experiment 2 elaborated that low-reflectance stimuli only produce a stronger Pulfrich effect than high-reflectance stimuli when the stimulus is moving away from the delayed eye. Data from the first two experiments were successfully captured by power law function fits and linearized by plotting Pulfrich effect strength against logit-Michelson contrast. Our third experiment revealed that increasing blur and dot count in the helix stimulus increased the likelihood of perceiving up or down motion. All three experiments in tandem show that investigating well-known visual illusions such as the Pulfrich effect in virtual reality has the potential to reveal insights into visual perception as well as inform us about the effects of contrast and asymmetric lighting in spatial computing.