Illusion-schmillusion. If I fits, I sits.

Recent study by citizen scientists furthers the notion that cats experience visual illusion like humans do.

Kausik Datta
6 min readJun 9, 2021
Under those watchful eyes… (Photo by author)

Engaged in a cupboard reorganization spree, we never anticipated it. S, my wife, was folding her purple woollen cardigan in order to stash it in a drawer. The cardigan has a woollen belt that runs through a solitary buckle at the back of the waist. The belt was on the bed, and I happened to lay it out in form of a closed circle. Whoosh! Our cat baby Widget Greything — the bitty hauspanther who is extraordinarily adept at Disapparating and Apparating at will — appeared right at the center of the circle, nonchalant, in a statuesque manner.

“Whoa! It’s true, what they say about cats and geometric shapes,” I exclaimed.

“Of course. There are studies that show this too,” S said. “But not all cats, though, you know. . .”

I knew exactly whom she meant: our other cat baby, Pudge Clementine, who has always been a bit. . . zen about everything around and shows little interest in gravitating towards circles and squares.

Not our Widget. Ever since he was a baby cat, Widget was never shy about demonstrating the at-once endearing and intriguing feline attribute of “If I fits, I sits.” (Apparently, even big cats, such as leopards, are not immune to the inscrutable charm of a small enclosed space.)

Widget has done this variously with the opened lids of carry-on or check-in sized suitcases; every time a delivery from Amazon arrives in a small, mid-sized, or largish cardboard box; the enclosed space made by joining two scratchy-couches; the hollow oval of the washroom basin; the lid of a freshly opened jigsaw puzzle box; and so forth. In our kitchen, he has plonked his fundament with great deliberation into the very small (and not at all cat-sized) enclosed area of a cloth bowl-hugger.

Six panels showing Widget Greything occupying enclosed spaces in various formats, lid of puzzle box, bowl hugger, washroom basin, luggage lid, cat scratchy-couch, and Amazon box.
Widget Greything in repose… inside enclosed shapes. (Photo by Author)

It, therefore, engendered a great deal of glee when I chanced upon Katherine Wu’s delightful article from last month’s issue of The Atlantic and immediately recognized in the author a kindred spirit sharing my wonderment re the mystery of feline fluidity. And we are certainly in good company there. As Katherine observed:

For all the hype that box-cats command, scientists still don’t fully understand why felines both big and small so fervidly flop their keisters into anything and everything.

Katherine Wu’s article, which I enjoyed very much, speaks of various competing theories attempting to explain this phenomenon, with quotes from various researchers who study animal behavior. Do go read it!

To me, the original study (published on April 30 in the journal Applied Animal Behavior Science) that sparked off Katherine’s piece held a special interest. Led by Gabriella Smith, an animal cognition researcher at Hunter College of CUNY, the study investigated whether domestic cats can perceive a shape illusion as a real shape and accordingly engage box/shape behavior. The shape illusion that was used is called a Kanizsa Square (see below for example).

Created by Italian psychologist and artist Gaetano Kanizsa (1913–1993), it is a visual illusion in which strategic placement of objects or shapes with sharply cut corners (referred to as “inducers”) creates the visual perception of the contours of a geometric structure-such as a square or a triangle-that is not there. Kanizsa’s structures are not the only examples of such illusory contours, and decades of research, including functional magnetic resonance imaging (fMRI) studies of the human brain, suggest that specific areas in the part of the brain that receives and interprets visual cues are responsible for these illusions.

Illustration of Kanizsa Squares used in the Study of visual illusion in cats led by Gabriella Smith, a researcher at Hunter College of CUNY.
Kanizsa Square (L), proper square as positive control (R) and non-square (M) as negative control in the Smith study; figure adapted from Table 2 for illustration.

In the Smith study, following instructions from the study team, citizen scientists — recruited via social media — performed the actual experiments in the comfortable environment of their own homes with their cats. The part that was the most interesting to me? Nine cats who participated in the complete study appeared to distinguish a real, physical square, as well as the perceived Kanizsa square, from a non-shape created by inverting the corner inducers of the Kanizsa square — showing a clear preference for sitting inside the real & perceptual squares!

Scientists refer to this phenomenon as “perceptual filling-in,” the connection that our brain makes to complete missing visual information. It happens naturally, without conscious thought; inside the eye, there are parts which cannot or do not respond to light falling on them, thereby creating data gaps, and the brain assiduously fills in the missing information about shapes, surfaces, and contours.

There is evidence that luminosity and contrast of the inducers (e.g., the corner Pac-man-like structures of Kanizsa Square) play an important role in the perception, and these studies have identified specific parts of the brain, as well as special types of brain cells, which are responsible for it. The ability to understand contours is considered a vital skill set that aids in making sense of the physical world around us.

Neurophysiological and behavioral studies done since the 1980s have confirmed the presence of this filling-in ability — which allows us to experience the visual illusions — in cats, dogs, mice, non-human primates, sharks, fish, honeybees, and owls, besides humans. Cats in particular, even though they are under no illusion about their god-like status amongst their humans, apparently encounter visual illusions in the same way as humans do, as understood from Kanizsa figure studies.

Of course, in the comments after Gabriella Smith’s announcement of the paper on Twitter, there were examples galore of cats which resolutely did not take part in anything remotely resembling these experiments, and their humans often wondered aloud if there was something “different” about their cats. For instance, as Twitter user Betty Jane graciously shared on Twitter:

Twitter user Betty Jane’s cat Doug is resolute in his refusal to find space inside a square, an act that is beneath his dignity.
Betty Jane’s Cat Doug appears to be one of those conscientious objectors to the indignity of having to park themselves inside geometric shapes, as shared by Betty Jane on Twitter.

For the 552 additional cats which were enrolled in, but did not complete, the study, I asked Smith if there was anything directly related to their personalities. “Not that we could tell,” Smith told me in a Twitter message. “The cats that didn’t finish the trials likely did so because their humans didn’t complete the six-trial-design of the experiment. This attrition taught us that lengthy experiments like this may not be ideal for the citizen science design as people have busy lives!”

For the redoubtable Doug, Smith reiterated to me the ageless aphorism learnt by humankind only through experience: “Cats will be cats.”

They certainly will be, especially if I go by anything like our other cat baby, Pudge Clementine, who would likely be one of those cats studiously avoiding geometric shapes, imaginary or otherwise.

Never one for being boxed in, our free-spirited Pudge Clementine occupies space in a fancy-free and footloose manner that nonetheless radiates dignity, he thinks. (Photo by Author)

Originally published at https://www.inscientioveritas.org on June 9, 2021.

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Kausik Datta

Wannabe storyteller in science. Graduate of John Hopkins Science Writing MA program.