Visual Illusions (also known as Optical Illusions) are experiences in which what we see does not correspond exactly with the true physical attributes of the object.
Visual Illusions are studied by physiologists, psychologists and other scientists for the clues they can provide about the workings of the eye and brain.
As well as their scientific interest, visual illusions can often be so remarkable that they may even cause us to question what we can know for sure about the world!
Explore the following links to discover some great optical illusions.
Müller-Lyer Illusion
The horizontal lines appear different lengths
Franz Müller-Lyer, Public domain, via Wikimedia Commons
Hall Checker Illusion
The checker board appears distorted
Blaine20, CC BY-SA 4.0, via Wikimedia Commons
Kanizsa's Triangle Illusion
There appears to be a white triangle
Fibonacci, CC BY-SA 3.0, via Wikimedia Commons
Ponzo Illusion
The left line appears longer than the right
Süle Krisztina, Public domain, via Wikimedia Commons
Zöllner illusion
The diagonal lines do not appear parallel
Fibonacci, CC BY-SA 3.0, via Wikimedia Commons
Delboeuf illusion
The black circles appear different sizes
CalendulaAsteraceae, CC BY-SA 4.0, via Wikimedia Commons
Fraser spiral illusion
Concentric circles appear as spiral
Mysid, Public domain, via Wikimedia Commons
Bezold effect illusion
The red lines appear darker on the right
Lockal, Public domain, via Wikimedia Commons
Poggendorff illusion
The black line appears to join the blue
Fibonacci, CC BY-SA 3.0, via Wikimedia Commons
Stepping feet illusion
The yellow and blue seem to move differently
Rinuraeni, CC BY-SA 4.0, via Wikimedia Commons