152 Visual Phenomena & Optical Illusions

with explanations

by Michael Bach

— Select one —

full tour stepping feet Motion Adaptation Reverse Phi Illusion snake snake snake Motion Induced Blindness Illusion Kinetic Depth Effect silencing Pinna-Brelstaff Pinna-Brelstaff2 Scanimation Roget Illusion Reverse Spoke Illusion wagon-wheel Illusion color wagon-wheel Illusion stroboscopic Illusion Sigma Illusion Eye Jitter Eye Jitter Relative motion Biological Motion flash lag Ramp Illusion Enigma freezing rotation radial stepping feet Motion Bounce Illusion Tusi Motion Breathing Square Illusion missingFundamentalIcon frequencyDoubling Icon kaleidoscopeIcon Ternus Icon SAM “Pigeon Neck” Psychokinematic Icon Dotted Lines Icon Motion Adaptation hermannGridIcon hermannGridCurvedIcon Grid Illusions Grid Illusions Moiré Moiré Pulfrich Classic simultaneous brightness contrast with probes 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 grid masking lum-shapeFromShading Ehrenstein disks coloured afterimgs watercolor Chromostereopsis 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 Color Change illusion icon Color from contour flankers icon Oblique Grating Oblique Grating adjustable Kinetic Orbison Illusion Tilted Table Hering Illusions Poggendorff Illusion Arch Illusion Frazer Illusion Tilt Illusion Cafe Wall Illusion Oblique grating simplest Checker Bulge Bourdon Illusion Jastrow Illusion Peripheral Curved Lines Illusion Triangle Puzzle Müller-Lyer Illusion Moon Illusion T illusion sine illusion luminance looming Shepard table shepard monster Size Constancy reverspective Necker Cube missing Corner Cube Ames Window silhouette illusion wireframe / silhouette Frankfurter Anamorphosis leaning towers Blind Spot Darwin Illusion Blur Illusion Blur Illusion Diamonds or squares Kanizsa Illusion Blotted Letter Illusion Dalmatian Hidden Bird Hidden object in brick wall Rotation Illusions Delboeuf Illusion Ebbinghaus Illusion Dynamic Ebbinghaus Illusion Pop-out in visual search Hollow Face Illusion Face on Mars Church or chicken Thatcher Illusion Ghostly Gaze blurred faces face mosaic face mosaic Motion Bounce Illusion Missing fundamental sound illusion

Some History / What’s new

2023-12-22  Xmas new colours

2023-09-10  kinetic Orbison

2023-07-10  update colour game

2023-01-07  simplest oblique

2023-12-22  Xmas new colours
2023-09-10  kinetic Orbison
2023-07-10  update colour game
2023-01-07  simplest oblique
2022-11-23  Diamonds/squares
2022-09-15  Relative motion
2022-03-01  Size Constancy
2021-12-16  curved lines
2021-12-16  Ehrenstein disks
2021-11-03  Bourdon
2021-08-07  revamped Roget
2021-06-19  wireframe / silhouette
2021-05-09  revamped contrast ad.
2021-02-14  Color from contour
2020-12-19  Pop-out
2020-08-16  improved Snake
2020-07-21  brightness probed
2020-07-13  shape from shading
2020-06-06  Chromostereopsis
2020-04-16  Missing fundamental
2020-03-29  Oblique adjustable
2019-12-14  Color Change illusion
2019-08-07  improved Palisade
2019-05-03  Grid masking
2019-04-23  Curving Scintillating Grid
2019-01-01  Rebuilt entire site in “Jekyll”
2018-12-29  This site uses no more Flash
2018-08-23  Colour Assimilaton
2018-06-03  New Numerosity
2018-06-03  New Bulge
2018-06-02  Site now in HTTPS
2018-05-29  New Jastrow
2018-05-13  3D silouette
2018-03-19  Contour & colour
2018-02-17  Update equilu
2017-08-09  Oblique Grating
2017-03-05  Red (?) strawberries
2016-12-21  White (?) Xmas
2016-09-13  12 black dots
2016-08-27  Snakes & luminace cntrl
2016-07-25  Acoustic Shepard
2016-07-18  Cube Corner
2016-07-17  Church or chicken
2016-07-07  Disjointed Arch
2016-05-21  Brick wall illusion
2015-12-28  New reverse phi
2015-12-05  New motion bounce
2015-11-27  New hidden messages
2015-11-20  Flash ≤ 10%
2015-07-25  Pulfrich Effect
2015-05-25  McCollough Effect
2015-04-25  New dynamic contrast
2015-04-25  Rotatory Moirée
2015-02-28  Colored-dress enigma
2015-02-15  Dotted Motion Illusion
2015-02-08  Psychokinematics
2015-01-06  Thatcher/Merkel
2014-12-28  Equiluminance
2014-12-07  Scanimation
2014-11-16  Watercolor
2014-10-28  Pinna-Brelstaff 2
2014-09-01  Pigeon Neck
2014-08-29  Hidden bird
2014-08-21  New Enigma
2014-08-16  New Induced Grating
2014-08-03  New COBC
2014-06-29  Colour Matching Game
2014-06-08  Colour Phi
2014-05-24  Dynamic Ebbinghaus
2014-04-26  Colour contrast
2014-02-05  Benham unrolled
2014-01-01  New Flash Lag
2013-12-26  Wagon-wheel/JavaScript
2013-12-25  Spokes in JavaScript
2013-12-23  Ebbinghaus
2013-12-20  Spiral MAE in JavaScript
2013-12-08  “Palisade” in JavaScript
2013-09-15  Tusi Motion
2013-07-12  Colour Fan
2013-06-05  new Pinna-Brelstaff
2013-04-23  Blind Spot
2013-03-16  improved M. Binding
2013-02-18  Ames Window
2013-02-09  Moiré Patterns
2013-02-03  snake ad lib
2013-01-19  Mach Bands
2012-11-21  Saccadic Suppression
2012-09-19  Contour Adaptation
2012-05-18  Colour Wagon Wheel
2012-05-07  Tilt
2012-05-01  Delboeuf
2012-04-13  Jastrow
2012-04-01  New Stepping Feet
2012-03-07  improved SAM
2012-03-04  improved Café Wall
2011-12-11  Leaning Towers
2011-11-13  Spine Drift
2011-11-13  New technology to replace Flash
2011-05-13  Motion silencing
2011-04-30  Tilted Table
2011-02-19  Impossible waterfall
2011-01-10  Munker Illusion
2010-10-17  Improved snak
2010-07-05  Numerosity
2010-04-15  Anamorphosis
2010-01-03  Shaded diamonds
2009-12-30  Checker Bulge
2009-09-17  SAM
2009-06-08  Breathing Square
2009-04-13  Colour mixing
2009-02-13  Darwin Illusion
2008-11-09  Ternus
2008-10-22  Necker cube
2008-10-03  symmetric silhouette
2008-05-13  reverspectives
2008-02-12  Triangle Puzzle
2008-01-02  Snake ad lib
2007-11-11  Ambiguous Silhouette
2007-10-20  Ghostly Gaze
2007-10-07  Hallucii
2007-07-13  Wagon-wheel
2007-03-18  Sine Illusion
2007-02-26  Helm's Kaleidoscope
2007-01-01  Roget's Palisade
2006-12-31  Spiral motion aftereffect
2006-09-24  floating Frankfurter
2006-08-27  Lazy Shadow
2006-07-26  Hidden Bird
2006-06-06  Gestalt & colour
2006-05-22  Freezing Rotation
2006-04-02  Hyperacuity
2006-01-01  cube illusion
2005-11-01  Angry & Smile
2005-10-19  Section Breaks
2005-10-03  Motion Binding
2005-10-01  Vasarely’s pyramid
2005-08-11  Terror Subterra
2005-07-23  eye jitter
2005-05-22  liac chaser
2005-04-24  Shepard’s table
2005-02-15  switched to CSS
2005-01-01  twisted Hermann grid
2004-12-21  frequency doubling
2004-12-12  Lincoln
2004-12-01  Luminance looming
2004-11-28  Missing fundamental
2004-10-18  Dalmatian
2004-08-16  T-illusion
2004-07-25  COBC
2004-06-25  impossible
2004-05-30  face on Mars
2004-05-16  face-in-beans
2004-04-14  checker shadow
2004-03-26  feet-lin
2004-03-08  Pinna-Brelstaff
2004-02-25  contrast gain
2004-02-08  Flash-Lag
2004-01-30  strobo artifacts
2004-01-03  rotating snake
2003-11-28  reverse phi text
2003-06-22  Poggendorff
2003-05-07  dynam. contrast (del.)
2003-04-18  Crossmodal
2003-02.12  no sex…
2003-02-11  Stereokinetics
2002-10-21  Neon
2002-10-12  MIB
2002-10-04  interactive M-W
2002-09-22  Café Wall
2002-09-08  sigma motion
2002-08-27  equiluminance
2002-08-16  Müller-Lyer
2002-08-11  animated Fraser
2002-06-28  White's illusion
2002-06-13  Adelson’s plaid
2001-06-05  Spoke rotation
1999-06-15  Hollow face
1997-04-13  First installment

Recognition, Awards (outdated)

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 here emphazises beauty and interactive experiments; I also attempt explanations of the underlying visual mechanisms where possible. Returning visitor? Check →here for History/News.

»Optical illusion« sounds derogative, as if exposing a malfunction of the visual system. Rather, I view these phenomena as highlighting particular good adaptations of our visual system to its experience with standard viewing situations, confronted with an atypical situation. These experiences are based on normal visual conditions, 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 an explanation seems gibberish, simply enjoy the phenomenon 😉.

What do illusions reveal about my personality?

Nothing! While the web is full of claims that your personality (right- or left brain dominated, intro- vs. extroverted, stressed or sublime, or whatnot…) can be deduced from your ability to see some given illusion or which variant for bistable ones. 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 don’t see them, mostly for reasons currently unknown.

More material

Bach & Poloschek (2006) Optical Illusions Primer (PDF, 2 pages from ACNR); on the programming: Bach 2014 (paywalled, contact me for a PDF).

Book (in German): “… Täuschungen … Sehphänomene”


Michael Bach (2022)
Optische Täuschungen und andere außergewöhnliche Sehphänomene
128 Seiten, 118 Abbildungen, Format: 240 × 170 mm
Preis: € 27,80,     ISBN: 978-3-942825-97-9,     Errata
Kaden-Verlag (Leseprobe) | Hugendubel | buecher.de | Amazon

Motion & Time

Luminance/Brightness & Contrast


Geometric & Angle Illusions

Space, 3D & Size Constancy

Cognitive / Gestalt Effects

Specialties with faces

Auditory Illusions

Donations to maintain this site

Some sources

My involvement with our local art society

Thanking Inga, who created new artwork (2005-04) for the ‘eyes’. More from the Bach Family: Maren.