134 Visual Phenomena & Optical Illusions

by Michael Bach ()

[other language: Deutsch]

— Click icon to select —

full tour stepping feet Motion Induced Blindness Illusion Kinetic Depth Effect, Autokinetic silencing snake snake snake Pinna-Brelstaff Pinna-Brelstaff2 Motion Adaptation, Waterfall Illusion Motion Adaptation, spiralling Scanimation Roget Illusion Reverse Spoke Illusion wagon-wheel Illusion color wagon-wheel Illusion stroboscopic Illusion Sigma Illusion Eye Jitter Eye Jitter Biological Motion flash lag Ramp Illusion enigma freezing rotation Reverse Phi Illusion radial stepping feet Motion Bounce Illusion Tusi Motion Breathing Square Illusion missingFundamentalIcon frequencyDoublingIcon kaleidoscopeIcon Ternus Icon Ternus Icon Ternus Icon Psychokinematic Icon Dotted Lines Icon hermannGridIcon hermannGridCurvedIcon Grid Illusions Grid Illusions Moiré Moiré Pulfrich Induced Grating Illusion Lozenges COBC Koffka Luminance Illusion Mach Bands Simultaneous Contrast Illusion Pyramid Illusion Munker-White Illusion Adelson Brightness Illusion checkerboard shadow saccadic suppression Contrast Illusion Contrast Illusion contrast gain control Lazy Shadow Vernier & acuity coloured afterimgs watercolor coloured afterimgs Colour Fan Benham Top Color Illusion Benham Top unrolled Colour Assimilation Neon Illusion Seasonal variant of White's illusion Neon Illusion Motion at equiluminance Gestalt at equiluminance Gestalt at equiluminance more equiluminance colour mixture colour matchin colour phi dress dress dress Oblique Grating Tilted Table Hering Illusions Arch Illusion Poggendorff Illusion Frazer Illusion Tilt Illusion Cafe Wall Illusion Triangle Puzzle Checker Bulge Jastrow IllusionMüller-Lyer Illusion Moon Illusion T illusion sine illusion luminance loomingI Shepard table shepard monster reverspective Necker Cube missing Corner Cube Ames Window silhouette illusion Frankfurter Anamorphosis leaning towers Blind Spot Darwin Illusion Blur Illusion Blur IllusionBlur Illusion Blotted Letter Illusion Dalmatian Hidden Bird Hidden object in brick wall Rotation Illusions Delboeuf Illusion Ebbinghaus Illusion Dynamic Ebbinghaus Illusion Hollow Face Illusion Face on Mars Church or chicken Thatcher Illusion Ghostly Gaze blurred faces face mosaic face mosaic Motion Bounce Illusion

Some History / What’s new

2019-01-01Rebuild of entire site
in “Jekyll”
2018-08-23Colour Assimilaton
2018-06-03New Numerosity
2018-06-03New Bulge
2018-06-02Site now in HTTPS
2018-05-29New Jastrow
2018-05-133D silouette
2018-03-19Contour & colour
2018-02-17Update equilu
2017-08-09Oblique Grating
2017-03-05Red (?) strawberries
2016-12-21White (?) Xmas
2016-09-1312 black dots
2016-08-27Snakes & luminace cntrl
2016-07-25Acoustic Shepard
2016-07-18Cube Corner
2016-07-17Church or chicken
2016-07-07Disjointed Arch
2016-05-21Brick wall illusion
2015-12-28New reverse phi
2015-12-05New motion bounce
2015-11-27New hidden messages
2015-11-20Flash < 10%
2015-07-25Pulfrich Effect
2015-05-25McCollough Effect
2015-04-25New dynamic contrast
2015-04-25Rotatory Moirée
2015-02-28Colored-dress enigma
2015-02-15Dotted Motion Illusion
2014-10-28Pinna-Brelstaff 2
2014-09-01Pigeon Neck
2014-08-29Hidden bird
2014-08-21New Enigma
2014-08-16New Induced Grating
2014-08-03New COBC
2014-06-29Colour Matching Game
2014-06-08Colour Phi
2014-05-24Dynamic Ebbinghaus
2014-04-26Colour contrast
2014-02-05Benham unrolled
2014-01-01New Flash Lag
2013-12-25Spokes in JavaScript
2013-12-20Spiral MAE in JavaScript
2013-12-08“Palisade” in JavaScript
2013-09-15Tusi Motion
2013-07-12Colour Fan
2013-06-05new Pinna-Brelstaff
2013-04-23Blind Spot
2013-03-16improved M. Binding
2013-02-18Ames Window
2013-02-09Moiré Patterns
2013-02-03snake ad lib: ØFlash
2013-01-19Mach Bands
2012-11-21Saccadic Suppression
2012-09-19Contour Adaptation
2012-05-18Colour Wagon Wheel
2012-04-01New Stepping Feet
2012-03-07improved SAM
2012-03-04improved Café Wall
2011-12-11Leaning Towers
2011-11-13Spine Drift
2011-11-13New technology to replace Flash, namely “Cappucino
2011-05-13Motion silencing
2011-04-30Tilted Table
2011-02-19Impossible waterfall
2011-01-10Munker Illusion
2010-10-17Improved Snake ad lib,
all pages hyphenated
2010-01-03Shaded diamonds
2009-12-30Checker Bulge
2009-06-08Breathing Square
2009-04-13Colour mixing
2009-02-13Darwin Illusion
2008-10-22Necker cube
2008-10-03symmetric silhouette
2008-02-12Triangle Puzzle
2008-01-02Snake ad lib
2007-11-11Ambiguous Silhouette
2007-10-20Ghostly Gaze
2007-06-08Added guestbook
2007-03-18Sine Illusion
2007-02-26Helm's Kaleidoscope
2007-01-01Roget's Palisade
2006-12-31Spiral motion aftereffect
2006-09-24floating Frankfurter
2006-08-27Lazy Shadow
2006-07-26Hidden Bird
2006-06-06Gestalt & colour
2006-05-22Freezing Rotation
2006-01-01cube illusion
2005-11-01Angry & Smile
2005-10-19added Section Breaks
2005-10-03Motion Binding
2005-10-01Vasarely’s pyramid
2005-08-11Terror Subterra
2005-07-23eye jitter
2005-05-22liac chaser
2005-04-24Shepard’s table
2005-02-15switched to CSS
2005-01-01twisted Hermann grid
2004-12-21frequency doubling
2004-12-01Luminance looming
2004-11-28Missing fundamental
2004-05-30face on Mars
2004-04-14checker shadow
2004-02-25contrast gain
2004-01-30strobo artifacts
2004-01-03rotating snake
2003-11-28reverse phi text
2003-05-07dynam. contrast (del.)
2003-02.12no sex…
2002-10-04interactive M-W
2002-09-22Café Wall
2002-09-08sigma motion
2002-08-11animated Fraser
2002-06-28White's illusion
2002-06-13Adelson’s plaid
2001-06-05Spoke rotation
1999-06-15Hollow face
1997-04-13First installment

Optical illusions don't “trick the eye” nor “fool the brain”, nor reveal that “our brain sucks”, … but are fascinating!

They also teach us about our visual perception, and its limitations. My selection emphazises beauty and interactive experiments; I also attempt explanations of the underlying visual mechanisms where possible.

Mobile user? It may help to rotate the display to landscape
Returning visitor? Check →here for History/News

»Optical illusion« sounds pejorative, as if exposing a malfunction of the visual system. Rather, I view these phenomena as highlighting particular good adaptations of our visual system to experience with standard viewing situations. These experiences are based on normal visual experiences, and thus under unusual contexts can lead to inappropriate interpretations of a visual scene (=“Bayesian interpretation of perception”).

If you are not a vision scientist, you might find my explanations too highbrow. That is not on purpose, but vision research simply is not trivial, like any science. So, if the explanation seems gibberish, simply enjoy the phenomenon 😉.
More here: Bach & Poloschek (2006) Optical Illusions Primer; on the programming: Bach (2014, PDF).

Can illusions reveal something about my personality?

No. The web is full of claims that your personality (right- or left brain dominated, intro- vs. extroverted, or whatever) can be deduced from your ability to see some certain illusion or not. However, there is no reliable scientific data that suggests this. That's just click-baiting BS. There is some influence of age, though –  but you don't need illusions to know your age… So: Don’t let it irk you if you don’t see all the phenomena described. For many illusions, there is a percentage of people with perfectly normal vision who just don’t see it, mostly for reasons currently unknown.

Motion & Time

Luminance & Contrast


Geometric- & Angle Illusions

Space, 3D & Size Constancy

Cognitive- / Gestalt Effects

Specialties with faces

Auditory Illusions


Some sources


My bread-and-butter job Klinik für Augenheilkunde, Universität Freiburg

My involvement with our local art society



Thanks to Inga who created new artwork (2005-04) for the ‘eyes’. More from the Bach Family: Maren, Oliver. Occasionally I update my PlusOne Blog.

Since 2018-12-29 Flash is no longer required to view anything on this site. Valid CSS! Valid HTML 4.01!