Ebbinghaus illusion (Titchener circles)
The Ebbinghaus illusion or Titchener circles is an optical illusion of relative size perception. Named for its discoverer, the German psychologist Hermann Ebbinghaus (1850–1909), the illusion was popularized in the English-speaking world by Edward B. Titchener in a 1901 textbook of experimental psychology, hence its alternative name "Titchener circles". In the best-known version of the illusion, two circles of identical size are placed near to each other, and one is surrounded by large circles while the other is surrounded by small circles. As a result of the juxtaposition of circles, the central circle surrounded by large circles appears smaller than the central circle surrounded by small circles.
Recent work suggests that two other critical factors involved in the perception of the Ebbinghaus illusion are the distance of the surrounding circles from the central circle and the completeness of the annulus, which makes the illusion comparable in nature to the Delboeuf illusion. Regardless of relative size, if the surrounding circles are closer to the central circle, the central circle appears larger and if the surrounding circles are far away, the central circle appears smaller. While the distance variable appears to be an active factor in the perception of relative size, the size of the surrounding circles limits how close they can be to the central circle, resulting in many studies confounding the two variables.
(Wikipedia)
Ebbinghaus illusion
Two circles of identical size are placed near to each other and one is surrounded by large circles while the other is surrounded by small circles;the central circle surrounded by large circles appears smaller than the central circle surrounded by small circles.
Explanation:
This is an illusion of relative size perception. The difference in size perception is due to the surrounding visual cues (larger or smaller surrounding circles), and the way the brain processes these visual cues.
The Ebbinghaus illusion has played a crucial role in the debate over the existence of separate pathways in the brain for perception and action. Experiments have shown that, while adult subjects perceive the center circles as differing in size, they reach out to grasp the circle accurately. In theory, this is due to the process of perception using a different visual pathway than the process of action. While adults rarely misjudge the size of the center disk while reaching for it, experiments have found that young children do, in fact, misjudge size both perceptually and through action. Researchers have proposed that this is because young children rely on both pathways to process tasks, instead of the separate pathways that adults use. (New world encyclopedia)
Additional evidence can be seen at: www.planetperplex.com Click on the image for the explanation.
The Dynamic Ebbinghaus:
The winner of the 2014 Best Illusion of the Year Contest: Ebbinghaus illusion in motion.
This can also be seen at www.youtube.com: The Dynamic Ebbinghaus and
illusionoftheyear.com Best Illusion of the Year Contest and 2014 Finalists
Delboeuf illusion
The Delboeuf illusion is an optical illusion of relative size perception. In the best-known version of the illusion, two circles of identical size have been placed near to each other and one is surrounded by an annulus; The surrounded circle then appears larger than the non-surrounded circle if the annulus is close, while appearing smaller than the non-surrounded circle if the annulus is distant. A 2005 study suggests it is caused by the same visual processes that cause the Ebbinghaus illusion.
It was named for the Belgian Philosopher, Mathematician, Experimental Psychologist, Hypnotist and Psychophysicist, Joseph Remi Leopold Delboeuf (1831 – 1896), who created it sometime in 1887 – 1888 (Wikipedia)
Two circles of identical size are placed near to each other and one is surrounded by an annulus; The surrounded circle then appears larger than the non-surrounded circle if the annulus is close, while appearing smaller than the non-surrounded circle if the annulus is distant.
Additional images can be seen at: www.moillusions.com alternate demonstrations.wolfram.com www.michaelbach.dePlate size and Delboeuf illusion
Image source: wikipedia