Reversible figure optical illusion — is it a duck or a rabbit? ...or a duck? ...or a rabbit?
The rabbit–duck illusion is an ambiguous image first published in the German humor magazine Fliegende Blätter in 1892. It can either be interpreted as the head of a duck (facing left) or a rabbit (facing right). Joseph Jastrow (1863–1944), an American psychologist, noted for inventions in experimental psychology, design of experiments, and psycho-physics, popularized this image and was once considered its creator. The German Fraktur text reads Welche Thiere gleichen einander am meisten? ("Which two animals look most alike?")—Kaninchen und Ente. ("Rabbit and duck.")