The video above was uploaded on YouTube by Rasmusab. The cat is looking at the rotating snake illusion. This is a powerful visual illusion created by the talented Professor Akiyoshi Kitaoka. Professor Kitaoka has created many remarkable visual illusions combining an artistic talent with a deep understanding of human vision. Professor Kitaoka’s website contains many other effective illusions some of which are produced using simple shapes.
What Might the Cat Be Seeing?
Does the cat see the illusion? We can’t know for sure but the cat paws at one and then another of the circles. When we look at the circles we see what Professor Kitaoka describes as an anomalous motion effect. The cat moves quickly as if trying to catch escaping prey. This happens repeatedly. Unlike us the cat is not quietly admiring a visual illusion but appears to believe that it is real and that what is seen demands immediate action. Since we see anomalous motion it is not too much of a step to take to assume that the cat shares our perception. We can not say for certain if the cat is seeing the illusion but is it possible to find better indirect evidence that the cat sees this as we do? When the cat stops pawing at the images this is even more interesting. We might think of habituation as an explanation. However it is also possible that the cat has gained insight into what is happening.
Does this mean that Cats might hallucinate?
Illusions are not hallucinations. Hallucinations occur in the absence of a sensory stimulus. Actually it is a little more complicated. When our eyes are open, the retina is receiving light from across the visual field. Therefore when hallucinations are seen we would expect that part of the visual field to also be receiving sensory input if the eyes are open. Therefore it is more sensible to say that the hallucinatory image and the sensory input from that part of the visual field are distinct and can be clearly distinguished from each other. In the above case we might think that the cat were hallucinating if it were pawing in the same way at a blank sheet of paper.
Does this tell us something about illusions in people?
The lineages of cats and humans diverged many millions of years ago. Both cats and humans are classified as placental mammals. A recent estimate suggests that humans and cats shared a common ancestor as recently as 65 million years ago. There are two ways that humans and cats might be able to see the same type of visual illusion. The first is where humans and cats have conserved features of our visual system after our divergence. The second possibility is that our visual systems developed very differently after our divergence. However at some point later on both species adapted to the environment and found the same ‘solution’ to an environmental problem but one which just happened to be caught out by the moving snakes illusion. This latter case is convergent evolution – where two species converge on the same adaptation to the environment. The first possibility is the most likely – visual adaptations that work would be conserved but would still remain susceptible to phenomenon such as the moving snakes illusion.
Professor Kitaoka has therefore produced an illusion that gives us insight into a feature of our visual system that has possibly been conserved for 65 million years. This may involve the Retina or parts of the Visual Cortex. This illusion also reminds us that we may share aspects of our conscious experience with cats and other animals.
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