“This is the depiction of the famous “duck-rabbit” figure, described as an “illusion” and attributed to Wittgenstein.
Technically, the duck-rabbit figure is an ambiguous (or reversible, or bistable) figure, not an illusion . The two classes of perceptual phenomena have quite different theoretical implications. From a constructivist point of view, many illusions illustrate the role of unconscious inferences in perception, while the ambiguous figures illustrate the role of expectations, world-knowledge, and the direction of attention . For example, children tested on Easter Sunday are more likely to see the figure as a rabbit; if tested on a Sunday in October, they tend to see it as a duck or similar bird.
But the more important point of this letter concerns attribution: the duck-rabbit was “originally noted” not by Wittgenstein, but rather by the American psychologist Joseph Jastrow in 1899 , when the famous philosopher was probably still in short pants. Along with such figures as the Necker cube and the Schroeder staircase, Jastrow used the duck-rabbit to make the point that perception is not just a product of the stimulus, but also of mental activity — that we see with the mind as well as the eye.”
– John F Kihlstorm