Young Girl-Old Woman Illusion

$\begin{figure}\begin{center}\BoxedEPSF{HagGirl.epsf scaled 500}\end{center}\end{figure}$

A perceptual Illusion in which the brain switches between seeing a young girl and an old woman.

References

Pappas, T. The Joy of Mathematics. San Carlos, CA: Wide World Publ./Tetra, p. 173, 1989.