Are the horizontal lines on the following figure parallel or do they seem to be skewed? They are indeed parallel but appear to run at angles because of the staggered black and white boxes. This illusion is commonly known as the cafe wall illusion.
Do you see a spiral in the image below? There is no spiral. This drawing consists of a series of concentric circles. This illusion, called the Fraser spiral was discovered by British psychologist James Fraser in the early 20th century.
Do the red lines below appear to bow outward? Or are they parallel? The red lines are straight and parallel and do not bow outward despite their appearance. This illusion, known as the Hering illusion, was discovered in 1861 by a German physiologist named Ewald Hering. The Hering illusion produces the opposite effect of the […]
Do the red bars appear perfectly straight and parallel? The lines are straight and parallel. Some viewers will perceive the lines to bow inwards due to the angles of the blue lines. This illusion was first observed by German psychologist Wilhelm Wundt during the 19th century. The Wundt illusion produces the opposite effect of the […]
These three horizontal lines are all the same length. Does the middle line appear to be longer than the top line? The arrows on the end of the lines give the impression that the lines are different lengths. The red horizontal lines help to show that they are all equal. This is known as the […]
In 1939, William Orbison described the following illusion where the red square appears to be distorted by the presence of the angled blue lines. It does not look to be a perfect square, but if you take a sheet of paper or something else with a straight edge and line it up, you will see […]
Do the black lines presented below appear to be parallel? The black lines are indeed parallel even though they do not appear to be. In 1860, this classic optical illusion was discovered by Johann Karl Friedrich Zöllner. This illusion was the basis for the discovery of the Poggendorff illusion.
