An distortion illusion devised
by the German "father of experimental psychology," and one-time assistant
to Hermann von Helmholtz at Heidelberg, Wilhelm Wundt (1832–1920).
In the figure, the two horizontal lines are both straight, but they look
as if they bow in at the middle. The distortion is induced by the crooked
lines on the background, as in Orbison's
illusion. The simplest of all distortion illusions – the horizontal-vertical
illusion (in which a vertical line looks longer than a horizontal line of
equal length) – was also discovered by Wundt.
AND IMPOSSIBLE FIGURES