You See a Glowing Centre. There is No Light There.

Which patch is lighter?

A is lighterSameB is lighter

You are looking at the Asahi illusion (named for the Japanese word for morning sun · 朝日), described by Akiyoshi Kitaoka and colleagues in the early 2000s. A set of radiating gradient spokes, each fading from dark at the outer edge to white at the centre, converges on a single central point. The central point appears to glow brighter than the surrounding white · you see a luminous, almost blinding centre. Measure the pixels at the centre and they are exactly the same white as the paper around it. There is no extra light. Your brain has invented a phantom light source.

What the Illusion Looks Like

Draw a circle. From its centre, radiate a series of spokes · each spoke is a narrow triangular wedge. Fill each wedge with a gradient that fades from dark grey at its outer end (at the circle’s perimeter) to pure white at its inner end (at the circle’s centre). Leave the background surrounding the circle as the same pure white that the spokes fade into.

The centre of the circle · where all the spoke-tips meet · appears to shine with a luminous, almost HDR-photograph brightness. The apparent glow extends beyond the geometric centre point, producing a “halo” effect. The physical white at the centre is identical to the white outside the circle.

Why It Works: The Brain Infers Glare

Your visual system has evolved to judge outdoor scenes. In natural scenes, very bright central regions surrounded by darker peripheral regions are almost always caused by a light source · the sun, a lamp, a fire. The visual system has learned this statistical regularity: converging gradient spokes fading to white = there is a light source at the centre.

The spokes’ gradient structure is the key cue. Each spoke fades from dark to bright toward the centre. This is the optical signature of glare: a bright light source scatters light around itself, producing a corona that is darker at its outer edge and brighter at its inner edge.

Your brain applies the glare prior. Gradient spokes + converging structure = light source + corona. The visual system infers that there must be a light source brighter than the paper white, and it renders the central region as if it were glowing.

The perception follows the inference. Your cortical representation of the centre is boosted above the physical pixel value. You see more brightness than is there, because your brain has inferred that a light source is hidden behind the page.

Why Digital Displays Amplify It

On a bright phone or laptop screen, the Asahi illusion looks particularly vivid · sometimes uncomfortably so, with a genuine sensation of glare. Why?

The Kitaoka Era of Illusion Making

Akiyoshi Kitaoka, a Japanese psychologist at Ritsumeikan University, has been perhaps the most prolific illusion-maker of the 21st century. His works · Asahi, Rotating Snakes, the Cycle-of-Grass · are widely shared online and have become a modern chapter in the illusion canon. Kitaoka’s distinctive approach: he generates hundreds of variants of each basic motif, tunes them for maximum effect, and publishes the best.

The Evolution Hypothesis

Why did our visual system evolve such a strong glare-inference prior? The evolutionary-visual-ecology answer: bright light sources with surrounding gradients are ecologically critical to detect and respond to. Predators and shade, sun and shadow, fire and safety · all have a strong dark-to-bright gradient structure. A visual system that automatically infers “there is a light source here” from such cues has a survival advantage: it prepares the pupil, redirects attention, and engages the motor systems for appropriate action.

A Harder Variant

Below is an Asahi figure at difficulty 3 · more spokes, a sharper gradient. The central region appears to glow blindingly. It is, as always, the same white as the paper.

Which patch is lighter?

A is lighterSameB is lighter

Where the Asahi Mechanism Matters

• Photography and HDR. Photographers composing sunburst shots through trees deliberately create gradient-spoke patterns to recruit the Asahi mechanism · the resulting photograph looks brighter and more luminous than its dynamic range would physically permit.
• Cinema lighting. Backlit scenes with haze and radiating light rays (crepuscular rays) are shot and staged to maximise the Asahi inference. The audience perceives the light source as “glorious” even when the camera’s sensor has captured nothing beyond ordinary brightness.
• Religious and mythic iconography. Sunbursts, halos, and radiance motifs in paintings and sculpture recruit Asahi-style inference. The Renaissance gold-leaf halo was a deliberate exploitation of the mechanism · viewers perceive the saint as literally glowing.
• Architecture and lighting design. Fixtures that produce radial gradient patterns on walls and ceilings induce Asahi-style glare perceptions. Architects use this to make modest lighting feel generous, or to create theatrical effects in galleries and sacred spaces.
• Digital UI. App launchers and notification popups that use radial-gradient backgrounds (think: Apple’s app icon glows, Google Material’s ripple effects) recruit a mild Asahi prior to produce a sense of luminosity without actually increasing pixel values.

Test Yourself on 50 More Illusions

The Asahi illusion is one of more than 50 classical illusions on PlayMemorize. Each round draws a deterministic SVG scene and asks one grounded question: which is larger, which is brighter, which is actually parallel. The reveal overlay shows the true geometry plus a one-line “why it works” caption.

• Keep playing Asahi → · the standalone game, pinned to this one figure with fresh seeds each round
• Play Illusions → · spot the tricks across size, colour, orientation, and impossible figures
• Play Spatial → · train mental rotation and area estimation
• Play Matrix → · abstract pattern reasoning under time pressure