Scientists Have Studied the Mysterious Behavior of Cats Sitting on Squares

Cats love sitting on any square object, as if drawn by some primordial instinct. A new study shows that the square can even be an optical illusion.
Scientists Have Studied the Mysterious Behavior of Cats Sitting on Squares
Image via Gabriella Smith
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Cats are notorious for crawling into any available small, enclosed space: boxes, laundry baskets, bins. And as many viral videos have shown, cats will even sit on flat square-shaped objects, to the internet's collective puzzlement. Now, new research has taken the first dive into examining the phenomenon. 

Researchers from City University of New York (CUNY) and the School of Psychology and Public Health in Australia set out to study cat cognition, and specifically whether they could perceive square-shaped optical illusions. They found that the box doesn’t need to be 3D to attract a cat: they’ll cozy up in a taped square or an optical illusion of a square, too. The study, called "If I fits I sits: A citizen science investigation into illusory contour susceptibility in domestic cats," was published on April 30 in Applied Animal Behaviour Science, an Elsevier journal. 


To study domestic cats in their natural habitat, the authors set up a citizen science investigation. A big reason that they used citizen science is that COVID-19 hit right when the research was set to start, according to Gabriella Smith, lead author on the study.

“We flirted with the idea of going to the lab, but it made more sense for people at home to do it,” Smith said. “Homes are more comfortable for cats.”

The team sent each participating cat-owner a box of materials to create three distinct shapes: a taped square, a Kanizsa illusion, and a control. A Kanizsa illusion is four “Pac-Man” shapes arranged so that the negative space forms a square. The control used the same Pac-Man shapes, but arranged face-out so that there was no illusion of a square.  

The cats sat in the Kanizsa squares and the taped squares, and didn’t sit in the control. According to the study, that means that cats are capable of “illusory-contour perception.” Illusory contours are visual cues that suggest the edge of a shape that doesn’t really exist. In this case, the Kanizsa illusion uses shapes to mark the corners of a square, and the brain fills in the rest of the shape. Humans develop illusory contour perception around 3 to 4 months, and it strengthens with age. 

“Many animals are evolved to perform this sort of perception,” said Smith. “It’s probably to do with navigating the environment. You need to know when not to walk into a tree or off a cliff.” 


Illusory-contour perception has been studied in many other species, but this is the first study that domestic cats are susceptible to illusory contours in an “ecologically relevant paradigm.” That is, a home, not a lab. 

As far as the authors know, this is also the first citizen science study of cat cognition, and the first formal examination into cats attraction to 2D rather than 3D enclosures.  

One struggle with using citizen science to track cat behavior is that many participants failed to complete the study. As intended, the study lasted for six days, with each day including a 5-minute trial. The cat-owning citizen scientists placed the cat in another room and laid out the visual stimuli, measuring precisely to ensure consistency. Then, they put dark sunglasses on (so as not to visually cue the cats) and let them back into the room. 

Out of 500 cats and owners, only 30 completed the entire trial, shrinking the sample size considerably. Within that sample size, the cats showed clear preference for the box-like illusions over the controls. Still, to further cat cognition research, the paper recommends future studies only require owners to perform the experiment for one day (rather than six) to increase likelihood of completion. 

Smith said that she’s also curious how this research would translate to non-domesticated cats like big, wild cats. 

“We don’t know whether wild cats are susceptible to that illusion, because they may not encounter corners and walls the same way,” Smith said.