Visual IllusionsVisual IllusionsDefinitionIllusions occur when what we see does not correspond to what is physically present in the world
Brightness After EffectBrightness After Effect
Please Stare for a whilePlease Stare for a while
Colour After EffectColour After Effect
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Please Stare for a whilePlease Stare for a while
Negative Colour After ImagesNegative Colour After Images
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Motion ContrastMotion Contrast
The Zöllner Illusion (Orientation Contrast)The Zöllner Illusion
(Orientation Contrast)
The Zöllner Illusion (Orientation Contrast)The Zöllner Illusion
(Orientation Contrast)
Object size is inferred from perceived distance and retinal image size
If 2 objects have the same retinal image size (i.e., are the same real size), the object appearing further away is seen as larger
Size-Distance RelationshipSize-Distance Relationship
Size-Distance RelationshipSize-Distance Relationship
The Ponzo IllusionThe Ponzo Illusion
Gregory’s theory
The visual system makes hypotheses about distance to objects based on evidence in the image. Interpretation of size follows.
Müller-Lyer IllusionMüller-Lyer Illusion
Müller-Lyer IllusionMüller-Lyer Illusion
0 5 10
Objectively equal in separation, perceptually different
0 5 10
Müller-Lyer IllusionMüller-Lyer Illusion
Perceptually equal in separation, objectively 30% different
0 5 10 15
Perspective cues set up false interpretations of distance
Müller-Lyer IllusionMüller-Lyer Illusion
Ames RoomAmes Room
Ames roomAmes room
Ames room sets up false distance cues
Objects that are different distances appear the same distance
Reversible Figure and GroundReversible Figure and Ground
Necker cubeNecker cube
Look at the red dot…
It can be either on a near corner or a far corner
Ambiguous figuresAmbiguous figures
Old woman looking down/young woman looking away
Ambiguous figuresAmbiguous figures
Ambiguous figuresAmbiguous figures
Rabbit
Ambiguous figuresAmbiguous figures
Duck
How many dolphins?How many dolphins?
Penrose TrianglePenrose Triangle
Escher’s printsEscher’s prints
The brain cannot compute 3-D structure from all parts at once, each part looks plausible in isolation
Escher’s printsEscher’s prints
The Thatcher IllusionThe Thatcher Illusion
This is the same stimuli but 1 looks more strange than other