A Ring of Lilac Dots. One Is Missing at a Time. A Green Dot Chases the Gap.
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You are looking at the lilac chaser illusion, first described by Jeremy Hinton in 2005. A ring of twelve lilac-coloured dots is arranged around a central fixation point. At any given moment, one of the dots is missing · hidden · and the missing position rotates around the ring approximately once every second. Fixate on the central point and two extraordinary things happen: first, the lilac dots fade away to grey (or disappear entirely), and second, a bright green dot appears, chasing around the ring · moving in the position where the missing lilac dot is. The green dot is nowhere in the ink. It is the colour-opposite afterimage of lilac, revealed because the surrounding lilac has been perceptually suppressed.
What you are about to learn. What the lilac chaser is, how it combines the Troxler fading effect with chromatic opponent afterimages, why fixation is critical, the cortical and retinal processes behind colour opponency, and how Hinton’s figure became one of the most-shared illusions on the early internet.
What the Illusion Looks Like
Draw 12 lilac (pale magenta-pink) dots arranged in a circle around a central black fixation cross. Each dot is roughly a centimetre across; the ring has a diameter of several centimetres. Now, program the display so that one dot at a time is missing · the missing position cycles around the ring clockwise, moving to the next position every 100 milliseconds or so.
Stage 1 · just look at it normally. You see 11 lilac dots with a gap moving around. Stage 2 · fixate on the central cross without moving your eyes. Within a few seconds, the lilac dots fade away to grey or vanish, and instead of lilac dots with a gap, you see a bright green dot chasing around the ring. The green dot is moving in the position where the lilac “gap” is. The colour is the chromatic opposite of lilac.
The minimal recipe. A ring of uniform chromatic dots (lilac works best) around a fixation point, with a rotating “gap” where one dot is absent. The animation must cycle around the ring fast enough that the Troxler effect (peripheral fading) can saturate the ring · typically 100-200 milliseconds per position. The dots should be in peripheral vision when the fixation cross is attended · not foveal. Lilac is important because its opponent colour (green) is bright and salient as an afterimage.
Why It Works: Troxler Fading Plus Chromatic Opponency
The lilac chaser combines two well-understood phenomena: Troxler fading (peripheral stimuli fade under fixation) and chromatic opponency (colour perception is based on opponent colour pairs).
Fixation causes peripheral adaptation. When you fixate the central cross, your peripheral retina is receiving steady input from the lilac dots · the same colour at the same location, cycle after cycle. Retinal and cortical neurons sensitive to lilac adapt (become less responsive) over time. Without fresh signal, the lilac percept fades.
The gap is unadapted. When the gap rotates to a new position, that position was previously showing lilac; now it is showing the background. Because the lilac-sensing neurons at that position are adapted, they now produce a signal in the opposite direction · a negative response, interpreted as green (the opponent colour of lilac).
The green afterimage chases the gap. Since the gap moves around the ring, so does the green afterimage. The lilac ring itself has faded because of Troxler’s effect, so the green is all you see · a bright green dot apparently chasing around the ring, with no surrounding lilac to compete.
Colour is a difference, not an absolute. Your visual system represents colours in opponent pairs · red vs green, blue vs yellow, white vs black. When one member of the pair adapts, the opposite is perceived with extra vividness. The lilac chaser exploits this: by adapting your peripheral lilac detectors, the non-lilac (green) signal at the gap position becomes positively visible. Colour is not an intrinsic property of light · it is a continually-computed difference signal that responds to adaptation. The green dot appears because your lilac detectors have gone temporarily silent.
A Harder Variant
Below is a lilac chaser at difficulty 3 · faster rotation, more dots. The green afterimage is more vivid.
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Common misconception: “the green dot is a pixel trick.” It is not. Screenshot the image at any moment and there is no green pixel · only lilac dots on a grey background, with one dot briefly absent. The green is entirely in your visual system. If you do not fixate the central cross, the effect diminishes or vanishes · because without fixation, the peripheral lilac does not fade, and without the lilac fading, the green afterimage is not revealed as a standalone percept.
The Role of Fixation
The lilac chaser is unusual among illusions in requiring sustained fixation to work. Most illusions are robust to gaze movement. The lilac chaser collapses without fixation.
Fixation as an experimental variable. Fixation lets the Troxler effect develop · adaptation of peripheral neurons takes several seconds to saturate. When you move your eyes, the stimulus shifts across the retina and the adaptation is reset · different neurons get exposed to the lilac, and none adapt enough to produce the green afterimage. The lilac chaser is therefore a real-time demonstration of the time course of retinal and cortical adaptation. Fixate, wait, see green. Look away, see lilac ring again. Repeat.
Hinton’s 2005 Discovery
Jeremy Hinton · a British vision researcher (and by trade a general practitioner) · published the lilac chaser online in 2005. It quickly spread through online illusion collections, science blogs, and visual-perception courses. The combination of simplicity (just a ring of dots with a rotating gap) and dramatic effect (green out of lilac, accompanied by the whole ring fading) made it one of the most-shared illusions of the early internet era.
An internet-age illusion. Many classical illusions were discovered in the 1800s by printing them on paper. The lilac chaser is a modern illusion · it requires animation (the gap must rotate) and is really only practical on a digital display. Its history is inseparable from the web: Hinton’s figure went viral on visual-perception mailing lists, cognitive-science blogs, and early YouTube videos. It has been analysed and cited in the vision literature more often than many older illusions · a reminder that the classical illusions collection keeps growing, especially when display technology enables new stimulus formats.
Related Afterimage Illusions
The lilac chaser is part of the afterimage illusion family · illusions that reveal the adapted state of the visual system after prolonged fixation.
The afterimage family. Lilac chaser: rotating gap in lilac ring produces a chasing green afterimage under fixation. Static negative afterimage: fixate any coloured patch for 30 seconds, then look at white · you see the opposite colour. Motion aftereffect: after staring at a moving pattern (rotating windmill, flowing water), a stationary scene appears to move in the opposite direction. Spiral aftereffect: a centre-expanding spiral, viewed for 30 seconds, makes subsequent stationary scenes appear to contract. All of these illusions demonstrate that your visual system continually adapts to prolonged input · and that the adapted state is revealed when the input changes.
Where the Lilac Chaser Appears
- Online illusion collections. Michael Bach’s Optical Illusions & Visual Phenomena (michaelbach.de) hosts an interactive version of the lilac chaser, widely cited in textbooks.
- Visual-perception lectures. The lilac chaser is a standard demonstration in university cognitive science and visual perception courses.
- Viral social media. Versions of the lilac chaser have been shared on Reddit, YouTube, and Twitter; it regularly cycles back into visibility.
- Clinical vision testing. Variants are used in testing macular pigment density and chromatic sensitivity · people with certain visual disorders may experience altered afterimages.
- Op Art-inspired animations. Some modern animated artworks exploit the lilac chaser mechanism to produce chromatic effects in peripheral vision that resolve only under steady fixation.
Test Yourself on 50 More Illusions
The lilac chaser 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 Lilac Chaser → · 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
The takeaway. The lilac chaser is a ring of lilac dots with a rotating gap. Fixate the centre and two things happen: the lilac ring fades away via Troxler’s adaptation effect, and a green afterimage · the chromatic opposite of lilac · appears chasing around where the gap is. The green dot is nowhere in the ink; it is generated by your visual system’s opponent-colour machinery when the lilac signal is adapted away. Jeremy Hinton published it in 2005 and it has become a staple of modern visual-perception demonstrations. The green is not in the screen. The green is in you.
Illusions
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שחקו עכשיו - בחינםללא חשבון. עובד בכל מכשיר.
