The Wundt Illusion is named for its discoverer, Wilhelm Wundt who is sometimes considered the first scientific psychologist.
In this illusion, the horizontal lines appear bowed away from the points at the top and the lines. The reasons for this illusion are not completely understood.
For our purpose, the interest, is how this illusion may play a role in how the triangular pediments at the end of roofs like on the Parthemon might be perceived. The shallow triangle of the pediments at the end of the roof of the Parthenon would tend to cause the bottom to appear bowed down like on the top horizontal line in the Wundt Illusion. Thus, the Parthenon is built with a shallow upward curve on the bottom of the pediment to compensate for this illusion.
To see the illustration in full screen, which is recommended, press the Full Screen button, which appears at the top of the page.
Below is a list of the ways that you can alter the figure. The settings include the following:
Number of Lines: You can change the number of lines used to draw the frame around the two horizontal lines from 2 to 40 in even number steps.
Height/Width: The ratio of the height of the figure (the distance from the two points where the lines start), the the width. The smaller this number the flatter the image, the larger, the more the height and the width are the same.
Line Height: The position of the horizontal line as a proption of the distance from the outside points to the middle. So the near to zero, the farther the lines are to the top and bottom. The closer this value is to one the closer the lines are to each other and to the middle.
Line Thickness: The thickness of the two horizontal lines in pixels.
Frame Lines: The thickness of the lines that make up the frame around the horizontal lines in pixels.
Direction: The direction of the figure. Horizontal has the illusion going from left to right. Vertical has the illusion going from top to bottom. Automatic will postion the figure so that it fits best on your screen.
Pressing this button restores the settings to their default values.