False Rotation
Move your head closer to the screen, then further away, while staring at the center. The rings will appear to rotate in opposite directions.
Motion from Self-Motion
🔄 The Pinna-Brelstaff Effect▼
Discovered by **Baingio Pinna** and **Gregory Brelstaff** in 2000. This illusion demonstrates how the brain integrates **Optic Flow** (the expansion/contraction of the image as you move) with local orientation cues.
📐 Geometry of Deception▼
The diamonds are tilted. As the image expands (when you move closer), the local motion vectors are radial (outward). However, the tilted edges of the diamonds bias these vectors, adding a rotational component.
Your brain solves for a vector that is a compromise between the radial expansion and the edge orientation, resulting in a perceived spiral motion.