Eye Test: Are these strawberries really red or gray? (Video) - Why these strawberries trick your brain into seeing two colors at once

A striking optical illusion has gone viral, showing strawberries that seem to shift between red and grey. The effect plays tricks on the brain, making the same fruit appear in two different colours. Scientists say it reveals how human vision works in unexpected ways.

The illusion was created by Japanese artist Akiyoshi Kitaoka in 2023. His video shows strawberries that look red at first glance but turn grey when viewed differently. The trick relies on color contrast and the brain's color constancy—a process where the visual cortex adjusts perceived colours based on lighting and surroundings.

Studies in Vision Research, including work by Coren and Ward (1989), explain why this happens. The brain interprets high-contrast edges as red when set against a lighter background, even if the actual hue hasn't changed. Experiments by neuroscientist Beau Lotto further confirm that human colour perception depends on surrounding luminance, not just the object's true colour.

The 'two-colour method' in the video pushes this effect even further. By altering the background and lighting, the brain separates what it expects to see from what's really there. Past experiences—like knowing strawberries are red—also strengthen the illusion, making the shift seem even more dramatic.

This illusion highlights how easily the brain can be fooled by context. The strawberries don't actually change colour, but the visual system fills in gaps based on assumptions. Researchers say it's a clear example of how perception doesn't always match reality.