One of the oldest ambiguous figures is the "Duck or Rabbit" This illusion first appeared in the October 23rd issue of Fliegende Blatter (a German humor magazine) in 1892. source.
The interesting thing about this illusion is that it is frequently credited to Joseph Jastrow 1899. Joseph Jastrow is an American psychologist who was the first to note this image in his work. He used the duck-rabbit figure 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 - source.
Jastrow's Cartoon (1899)
The truth though is that while Jastrow used his image in 1899 it had appeared in print at least twice before both times in 1892.
Jastrow's 1899 cartoon version was based on one originally published in Harper’s Weekly (November 19, 1892, p. 1114). The Harper's cartoon, in turn, was based on the original in Fliegende Blatter.
Below is a new version of this old favorite...
The photographer found this version during a visit to the Ripley's Believe It or Not! museum in Branson, Missouri.
What do you see a duck (looking left) or a rabbit (looking right). If you slide your mouse over the image the photo will rotate giving you a slightly differ perspective.
Flickr Artist: Dropped_Stitch
So what did you see in this image a duck or a rabbit? Which version above is most effective for you?
There are an endless variety of this type of illusion. What other ambiguous optical illusions have you seen?