Visual Phenomena & Optical Illusions

Motion & Time

• »Stepping feet« illusion 1 – strong, beautiful and (relatively) easy to understand
• Motion Induced Blindness – an illusion of disappearing dots
• Stereokinetic Phenomenon – an optical illusion of 3D from motion (aka »kinetic depth effect«)
• Motion silences hue changes – winner of the illusion contest 2011
• »Rotating Snakes« Illusion – with a new explanatory twist
• Snake ad lib – optimising this motion illusion
• “Rotating Snakes” – with luminance control
• Pinna-Brelstaff Illusion
• Pinna-Brelstaff Illusion #2
• Motion Aftereffect – also known as »waterfall effect«
• Spiral Motion Aftereffect – more effective for some
• Kinegram (“Scanimation”) – akin to a flip book
• Roget's Palisade Illusion
• Spoke Illusion – a motion illusion + an unexpected (?) aftereffect
• Wagon-wheel effect – closely related to stroboscopic artifacts
• Wagon-wheel with colours
• Stroboscopic Artifacts – making a teaching point out of a nuisance
• Sigma Motion – an optical illusion due to an interaction of image dynamics and eye movements
• Spine Drift illusion – more on eye movements, involuntary ones
• Eye Jitter – and even more on involuntary eye movements
• Biological Motion – for me the most beautiful class of visual illusions
• Flash-lag Effect – moving and stationary objects perceived at different times
• Ramp Aftereffect – an aftereffect in time
• Enigma (Isia Leviant)
• Freezing Rotation Illusion – a “Best Illusion of the Year” winner
• Reverse Phi Motion – something for the specialist
• »Stepping feet« illusion 2 – circular version of »Stepping feet 1«, weaker
• Motion Binding
• Tusi Motion
• Breathing Square
• Missing-fundamental motion inversion
• Frequency-doubling illusion
• »Kaleidoscope Motion« Illusion
• Ternus Display
• Stroboscopic alternative motion
• “Pigeon Neck” illusion
• “Psychokinematic” objects
• Dotted Lines motion illusion

Luminance & Contrast

• Hermann’s Grid – fleeting luminance illusions
• Hermann’s Grid bent – a new twist, refuting the classical explanation
• Scintillating Grid – strong fleeting luminance illusions
• 12 Vanishing Dots – No variation of the above
• Translational Moiré Patterns
• Rotatory Moiré Patterns
• Pulfrich effect – luminance turning time into displacement → stereo
• Induced grating – classical brightness contrast
• Shaded-diamond illusion – more brightness contrast
• Craik-O’Brien-Cornsweet – collaboration of retina & cortex
• Wertheimer-Koffka-Ring – pitting Gestalt vs. lateral inhibition
• Mach Bands
• Simultaneous Contrast – here dynamic
• Pyramid Illusion – Vasarely revealed
• Munker-White Illusion – contrary to lateral inhibition
• Adelson’s »Corrugated Plaid« – context affecting brightness
• Adelson’s »Checker Shadow« illusion – more context affecting brightness
• Saccadic Suppression – eye movements interact with visibility
• Contour Adaptation – a new case of contrast gain control
• Contrast Constancy – demonstrating space-average-based contrast gain control
• Contrast Gain Control – demonstrating temporal contrast gain control
• Lazy Shadow – Interaction of luminance & time
• Visual Acuity ↔ Hyperacuity

Colour

• Hinton's »Lilac Chaser« – a strong aftereffect, colours move which aren't really there
• Watercolor Illusion – long-range colour induction
• Context affects colour – different eyes?
• Colour Fan – more aftereffects
• Benham’s Top – colour from spatio-temporal patterns
• Benham’s Top “unrolled”
• Colour Assimilation
• Neon Colour Spreading
• White (?) Xmas –  a seasonal variant of White's illusion
• Munker Illusion
• Structure from motion – fails at equiluminance
• Loss of countour in colour
• Gestalt loss in equilumance
• Equiluminance: Heterochromatic flicker fustion & minimum motion
• Colour mixing – additive and multiplicative
• Colour matching – a game
• Colour Phi
• Dress-Color enigma
• Red Strawberries that are not red – strong demo of colour constancy
• McCollough Effect – an aftereffect that can last months

Geometric- & Angle Illusions

• Skye’s Oblique Grating – No Café Wall variant
• Tilted Table – a cute Zöllner variant
• Hering Illusion – and other angular interactions
• Poggendorff Illusion – a classical geometric optical illusion with a new twist
• Disjointed Arch Illusion – a strong Poggendorff variant
• Fraser’s Spiral
• Tilt Illusion
• »Café Wall« Illusion
• Triangle Puzzle – a puzzle, but an illusion too
• Checker Bulge
• Jastrow Illusion – a classic, unexplained

Space, 3D & Size Constancy

• Müller-Lyer Illusion – test your bisection accuracy
• Moon illusion
• T-illusion
• Sine Illusion
• Schäffel's Luminance Looming
• Shepard’s “Turning the Tables”
• Shepard’s “Subterranean Terror”
• Reverspective – reverse perspective
• Necker Cube – the mother of reversible figures
• Missing Corner Cube – a cube with multiple ambiguities
• Ames Window
• Ambiguous Sillouette Illusion
• Frankfurter Illusion – binocular rivalry & supression
• Anamorphosis
• Leaning Towers Illusion

Cognitive- / Gestalt Effects

• Blind Spot – intelligent fill-in
• Darwin Illusion – the afterimage creates a recognisable Gestalt
• Blur & picture content – spatial filtering (or high frequency masking)
• Hidden message – blur & figure-ground discrimination
• Kanizsa’s Triangle – depends on context
• Blotted letters – Gestalt completion
• Hidden Figures – Dalmatian Dog with 2 helpers
• Hidden Bird – more camouflage
• Hidden object in brick wall
• Rotation – changes the interpretation
• Impossible Objects – draw your own impossible object
• Hallucii – An “impossible” movie
• Impossible waterfall – Another Escher inspiration
• Numerosity adaptation
• Delboeuf Illusion – with an application to eating
• Ebbinghaus Illusion
• Dynamic Ebbinghaus Illusion

Specialties with faces

• Rotating face mask – hollow faces
• Find the Face (in the Beans) – a picture puzzle
• The face on Mars – imaginations of perception
• Church or chicken?
• The »Thatcher Illusion« – inverted faces lose their emotional message
• »Ghostly Gaze« Illusion
• Dr. Angry and Mr. Smile – two messages in two spatial frequency bands
• The Lincoln Effect

Auditory Illusions

• Shepard Tone
• Motion-Bounce Illusion – sound influencing perception of motion (crossmodally)

Some sources

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

My involvement with our local art society