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Is The Cat Going Up The Stairs Or Down The Stairs? Let The Debate Commence!


(PCM) You may remember the case of the infamous “blue dress” image that sent the internet into a tizzy of debate as to what was the actual color of the garment. Was it blue/black or white/gold?  The optical illusion certainly had people split 50/50 on both sides of the argument.

A new image of a cat that was posted on has stirred up a similar debate across the internet, as many people are confused as to whether or not the cat is going up or down the set of stairs.

We discovered one possible theory surrounding the cat photo courtesy of Nick Carter, a Professor of Behavioural Science at Warwick Business School.

Professor Chater said: “We see in 3-D, even though our eyes only receive 2-D images. This seems puzzling, because, it can be shown mathematically that there is an implied number of 3-D scenes that will create the same 2-D images.

“Most of the time, our brain is spectacularly good at solving this problem – it usually turns out that, precisely one 3-D interpretation is ‘sensible’ and all the others are bizarre, in one way or another.

“A classic visual illusion, the Ames rooms (​) shows this very neatly. We look through a peephole on one side of what appears to be a perfectly normal rectangular room, but it is in fact a bizarre stretched-out shape, carefully designed to project just the same 2-D image as a normal rectangular room would (And, in fact, there is an infinite number of weird shaped Ames rooms that would fool us just as well).

“So our brain uses the most ‘sensible’ 3-D interpretation; and mostly (except when we are being subjected to cunning visual illusions) this works just fine. But sometimes there are two equally plausible 3-D interpretations of the same 2-D image. Famous examples include the Necker cube ( and Rubin’s face-vase illusion ( ​Then, the brain flips between one interpretation and the other.

“So why does the ‘cat on the stairs’ picture have two interpretations? The key is the amorphous grey square at the top of the picture. Consider the angle between the plane of the staircase and the surface represented by this grey patch.

“When we see the cat as coming downstairs, the grey square is interpreted as ceiling – and this makes an acute, roughly 45 degree, angle with the staircase.

“But when we see the cat as going upstairs, the grey square is now interpreted as floor – and this makes an obtuse, roughly 135 degree angle with the staircase.

“If we could only tell the ‘slant’ of the mysterious square patch in relation to the staircase we would know if it was floor or ceiling, and so there would be no ambiguity. But the image cleverly leaves the grey square bereft of any clues. So we flip from one interpretation to the other.”

There you have it ladies and gentlemen!  Happy debate!

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