'If I Fits I Sits': The Science Behind Cats Sitting in Squares

cat in box — Cats are drawn to boxes, as any cat lover can attest. But why? Nobody really knows. Chris Winsor/Getty Images

It's common knowledge that if an empty box of any size is left unattended and a cat finds it, that cat will sit inside. Tiny cats in large boxes, large cats in tiny boxes — doesn't matter. "If I fits," the cat says in its little cat brain, "I sits."

Anyone who lives with a cat has seen this happen. And it doesn't even have to be a box; it turns out any square will do. A piece of paper, a laptop, anything rectangular seems to light up that box-sitting instinct in housecats. In 2017, the Twitter hashtag #CatSquare highlighted this cat quirk. Merely taping an empty square on the floor was enough to lure a cat to sit or lie down inside it.

A couple of years later, this hashtag would help animal psychology researcher Gabriella Smith at Hunter College, City University of New York, construct an experiment to gauge cat cognition. In April 2021, her research, entitled "If I Fits, I Sits: A Citizen Science Investigation Into Illusory Contour Susceptibility in Domestic Cats," was published in Applied Animal Behaviour Science.

Does the Box Have to Be Real?

Smith had seen #CatSquare on Twitter and knew that cats would sit inside a 2D square made of tape, not just inside a 3D box. "So then the question became, does the square actually have to be there?" Smith says.

"When we ask, 'What is this animal seeing?' people think of using dogs because they're so easily trained," Smith says. "But cats are the perfect candidate because we already know they will sit in a 2D square." Not only do cats not have to be trained to do this, they don't even have to come into the lab to do it. Cat owners (or as cats call them, servants) could easily tape shapes to the floor and record their cats' reactions.

Thus the first cat cognition experiment to use citizen scientists was born. And what better timing than during the COVID-19 pandemic? Smith put out the call for volunteers (via Twitter, of course) in June 2020. Much of the world was on lockdown to some degree, and cat owners were looking for something — anything — to do in their homes. Plus, Smith notes, "Cats perform best at home. In the lab, they wouldn't behave naturally."

cat in square — Ash is seen here sitting inside a Kanizsa square. Her owner, Tara McCready, participated in the citizen science study and took the photo.
Gabriella Smith

The Experiment to Find Out

She designed the experiment so the humans could gather cat data over six days. Participants were given templates to print out: a square to tape on the floor, and a set of "Pac-Mans," as Smith calls them, that could make an illusory square. Officially, this is called a "Kanisza square," which means that pieces of an image construct a complete image in our brains. Our minds see an image, in this case of a square, in the negative space.

So if you face the Pac-Mans with their mouths toward each other, there's an illusion of a square on the floor. Our eyes connect the dots. If you face their mouths away from each other, we don't perceive any significant shape. Would cats see the same things?

Smith went into the experiment with frankly low expectations and an open mind. She was truly curious to know the answer to her question: Will cats sit in a square that isn't really there? She had no preconceived ideas for what the cats might choose to do. She says that was helpful in designing the experiment, as her biases for one shape or another weren't in play. "I was lucky I had any participants at all, given how cats are."

The Results

She gathered data over the summer of 2020, with participant humans sending in five-minute videos of the shapes on the floor. If the cat positioned its body within any of the shapes for at least 30 seconds, it counted as a data point. Of course, cats are cats. "I watched a lot of empty videos," Smith says. Sometimes the cat would saunter through the video without sitting at all.

Smith recruited 500 participants, and 30 were able to complete the entire six-day sequence of tests. Of those, nine cats chose at least one of the shapes by sitting inside it — with all four feet — for at least three seconds. Though the data set is small, cats did indeed choose the Kanisza square illusion as often as they chose the complete square taped on the floor. They chose both of these more often than the non-shape made by the Pac-Mans facing away from each other.

While this was Smith's first time using citizen scientists to gather data, she has since been involved in another half-dozen citizen science studies with dogs in the Animal Behavior and Conservation Program at Hunter College.

She notes that you don't have to have the cleverest animal in the world to participate in projects like this. "All you have to do is follow instructions." Then just let your pet do its thing. Or not. It's all data. Science!

This research might seem pretty low stakes to some people, but it offers new insight into animal cognition and psychology. We now know that cats can connect the dots and see a square that isn't there. It's also a springboard for more potential research. "We see videos from zoos of large cats sitting in boxes, which makes sense because it's safe like a cave or den," Smith says. But would a wild cat sit inside the outline of a square? Or a Kanisza square that isn't a square at all?

This is the fun part of science: Asking questions and devising ways to learn the answers — and then letting those answers inspire new questions.