Do carrots actually help you see in the dark?

Only if you are deficient in vitamin A. Carrots supply beta-carotene, which the body converts to the vitamin A used to build rhodopsin, the retinal pigment for low-light vision. But if your diet is already adequate, extra carrots do nothing to improve your eyesight.

Why did Britain say carrots help night vision during World War II?

Britain had a surplus of roughly 100,000 tons of carrots by 1942 and needed people to eat them. The Ministry of Food's Dr Carrot campaign promoted them as an aid to seeing during nightly blackouts, a claim that was exaggerated but rooted in real biology.

Was the carrot myth really propaganda to fool Nazi Germany?

No. Historians found no evidence the campaign was aimed at Germany, and the Germans already had their own radar, so there was no secret to hide. The carrot campaign was a domestic effort to feed Britain and clear a vegetable surplus.

Why do optical illusions work?

Optical illusions work because vision is not a passive recording but an active reconstruction. The brain receives ambiguous, incomplete signals from the eyes and fills in the rest with its best guess based on past experience. Illusions are engineered to make that guess go wrong in predictable ways.

Are optical illusions a trick of the eye or the brain?

They are a product of the brain, not the eye. The eye accurately records the light that reaches it. The distortion happens afterward, in the visual cortex, where the brain interprets that raw data using built-in assumptions about depth, light, and shadow.

Why does everyone see the same optical illusions the same way?

Because humans share the same visual hardware and the same physical world. Light falls from above, objects shrink with distance, and shadows behave consistently. The brain's shortcuts are tuned to these universal regularities, so a well-built illusion fools almost everyone.

Do people actually see colors differently from each other?

Yes. Genetic variation tunes each person's cone cells slightly differently, roughly 8 percent of men have red-green color deficiency, and language influences which color differences we notice. Whether two people share the exact same private sensation of a color is impossible to verify.

Is color a real property of objects or made by the brain?

Light itself carries no color, only wavelengths. Color is constructed inside the brain from the signals of three types of cone cells in the eye. It is an inference, not a fixed property of the object being viewed.

Why did people see the dress as different colors?

The photograph was ambiguously lit, so each brain guessed at the illumination and subtracted it. Brains that assumed cool blue light saw white and gold; brains that assumed warm light saw blue and black. Same pixels, different internal guesses.

Why did people see The Dress as different colors?

The photograph was ambiguous about its lighting, so each viewer's brain guessed the illumination differently. Brains that assumed cool daylight subtracted blue and saw white and gold; brains that assumed warm indoor light subtracted yellow and saw blue and black. Both were applying normal color constancy.

What color was The Dress actually?

The physical garment, sold by the British retailer Roman Originals, was blue and black. But the viral photograph was genuinely ambiguous, so there was no single correct color to see in the image itself, even though the real fabric was blue and black.

What is color constancy?

Color constancy is the brain's ability to perceive an object's true color regardless of the lighting on it. It measures the color of the ambient light and subtracts it, so a white shirt looks white in both blue daylight and warm indoor light.

Why can't you see your own blind spot?

Your brain fills in the missing region using detail from the surrounding area, a process called perceptual filling-in. It also has two eyes whose blind spots fall in different places, so each eye covers the gap the other one misses. You experience the result as a seamless, complete scene.

What causes the blind spot in your eye?

The blind spot is where the optic nerve exits the back of the eye through the optic disc. At that exact point there are no rods or cones, the light-detecting cells, so that small patch of the retina cannot register any light at all.

How big is the blind spot in human vision?

Each blind spot covers roughly five to seven degrees of the visual field, sitting about fifteen degrees off-center. That is large enough to hide around nine full moons placed side by side, or even a person's face across a room.

— UNTOLD · Filed under

vision

All essays in .

All essays filed in this edition, newest first.

UNTOLD · Plate · NO. P01

The Mountain of Carrots That Fooled the World

Britain's wartime carrot myth had nothing to do with spies and everything to do with a surplus nobody could eat.

By D. Kile — 15 Aug 2026

UNTOLD · Mind · NO. M01

The Controlled Hallucination Behind Everything You See

Optical illusions are not failures of the eye but glimpses of the brain doing its ordinary, extraordinary work.

By J. Miro — 24 Jul 2026

UNTOLD · Mind · NO. M01

The Private Color Inside Your Head

Light carries no color of its own. Everything you see is a guess your brain paints from scratch.

By J. Miro — 22 Jul 2026

UNTOLD · Mind · NO. M01

The Photograph That Proved You Don't See the World

A blurry snapshot of a cheap dress became the largest perception experiment ever run by accident.

By J. Miro — 03 Jul 2026

UNTOLD · Mind · NO. M01

The Hole You Will Never Find

Every eye carries a patch of nothing, and the brain spends every waking second painting over it.

By J. Miro — 17 Jun 2026