The Pulfrich Effect in Virtual Reality
Anthony LoPrete, Alexander M Gokan, Arthur Shapiro · ACM Transactions on Applied Perception · 2025
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 and contrast on the Pulfrich effect in VR and on the perception of motion. In two of our 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. Our second experiment extends the first with a discrimination task and a larger number of observers, confirming that low-contrast low-luminance conditions produce distinct perceptual effects. Experiment 3 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 and third experiments were successfully captured by power law function fits and linearized by plotting Pulfrich effect strength against logit-Michelson contrast. We use the power law as a basis for a fifth section discussing a potential model that may explain computationally how luminance and contrast contribute to the magnitude of the Pulfrich effect. All three experiments and the modeling section in tandem show that investigating well-known visual illusions such as the Pulfrich effect in VR 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.