The rabbit-duck illusion

“Which animals are most like each other?” The original rabbit-duck illusion,
by an unknown author (see text).

In my blog last week, I used the rabbit-duck illusion, as it is usually called, to explain that there are two ways of looking at. Actually, the figure is not an illusion but an ambiguous image: It doesn’t evoke a false way of seeing but the image can be seen in two different ways that as such are correct. The figure has been made famous by Wittgenstein, who used it for explaining the difference between “seeing” and “seeing as”. When someone shows you the figure, you can say, for example: “I see a rabbit”. However, once you know that the figure is ambiguous and you can switch between the rabbit and the duck, you’ll say: “I see it as a rabbit”. Once we can see an image in different ways, we can notice aspects of the image, so Wittgenstein (Philosophical Investigations, ix). This noticing of aspects is a theme that again and again returns in his later work.
Wittgenstein took the figure from an article by the American psychologist Joseph Jastrow, but the image was first published in 1892 in the German humour magazine Fliegende Blätter, which described it as “Rabbit and Duck” (see picture above). Also Jastrow talked about a rabbit and a duck, but in the original German version of the Philosophical Investigations (PI) Wittgenstein says that the image can be seen either as the head of a hare (Hase) or as the head of a duck (Ente). However, in the English version of PI this is translated as a rabbit-duck distinction. Why this difference? In view of the long ears, I would call the animal in the image a hare rather than a rabbit, and when I am running through the woods and fields around my town I am sure whether I see a hare or a rabbit.
Be it as it may, let me further call the animal in the figure a rabbit in agreement with the present usage. The image is not only philosophically and linguistically but also psychologically interesting. As psychologists know, seeing and watching are not spontaneous and not objective. One has to learn it. So one question is: How do children see the image? Alison Gopnik and her colleagues (source) tried to answer this question, and they found that 3-5 years old children don’t make the reversal between two aspects of an ambiguous image on its own. Others must tell them that it has two aspects. Only later some learn to switch spontaneously. Also the speed of switching between the rabbit and duck aspects is interesting: R. Wiseman and his colleagues found that more creative people find it easier to switch between the rabbit-duck aspects of the image than less creative people do. (source) I wonder whether this result depends on the ambiguous image you take for a study. Personally I find it easy to flip between the rabbit and the duck but difficult to do so in case of the old woman – young woman illusion (see here).
Also when you look at the rabbit-duck image has an impact on what you see. Peter Brugger and Susanne Brugger showed the image to different people, first on an Easter Sunday and later that same year on an October Sunday, and simply asked them to name the animal. This is what they found: “Whereas on Easter the drawing was significantly more often recognized as a bunny, in October it was considered a bird by most subjects…” (some mentioned another animal than a duck, such as a stork, a flamingo, or just “some kind of bird”) (source)
Seeing and watching are not objective, as said. The discussion about the meaning of the rabbit-duck illusion shows that we can see what we see in different ways. Even more, we don’t see only with our eyes but a big part of the process of seeing takes place in the brain. Impressions of light arrive in the brain and with the help of the information already present there, the brain constructs a picture and gives it a meaning at the same time. Actually the interpretation (meaning giving) and the construction of the picture are one process. However, the brain can also make construct pictures without an external input through the eyes, and actually it often happens. Therefore seeing – in the limited sense of receiving input through the eyes – is important, for although the construction of the picture takes place in the brain, what you see does have an impact, and if you cut off your brain from the world, it’s quite well possible that you keep a rabbit for a duck, or the other way round.