Hering Illusion

Overview

The Hering illusion has long captured the imagination of both scientists and artists, revealing how easily our perception of space can be distorted. When two perfectly straight vertical lines are placed over a field of radiating lines, they appear to curve outward even though they remain parallel. First described by Ewald Hering in 1861, the effect has been studied through various lenses, some attributing it to angle exaggeration in the brain, others linking it to neural activity in the visual cortex. More recent interpretations suggest the illusion reflects our brain’s attempt to predict motion and depth, crafting a mental image of what the world might look like a moment later.

Mark Changizi offered a powerful explanation when he said that geometric drawings like this evoke premonitions of the near future. The converging lines mimic the experience of walking forward, as if passing through a hallway or doorway where the vertical edges seem to bow outward. It is a reminder of how easily our minds shift into a future that does not exist yet. In daily life, we often live ahead of ourselves, projecting into what is next, trying to foresee outcomes, opportunities, or dangers. But like the illusion, that future is just a construction, and sometimes the cost of looking ahead is missing what is directly in front of us. The Hering illusion becomes not just a perceptual trick but a quiet lesson in presence.

The code used to render this illusion begins by drawing blue radial lines from the center, spaced five degrees apart, to create the sensation of outward motion. Afterward, two red vertical lines are placed on either side. Though mathematically straight, they appear warped against the radial field. The turtle module handles the drawing, rotating the cursor to trace the radiating pattern, while the Pillow library captures and converts the final image. The illusion emerges not from complexity but from precision — lines, angles, and symmetry arranged to provoke misperception. The visual result reveals how a few calculated steps in code can create something that challenges how we see both space and time.

You can find my code repository here.