“If I Fits, I Sits:” Why Do Cats Love Boxes (Fake Ones, Too)? | Catzio

“If I Fits, I Sits:” Why Do Cats Love Boxes (Fake Ones, Too)?

Saving yet another Amazon box for your cat? You might not have to this time! Gabriella Smith, M.A. and colleagues have expanded on past research, showing that your pet cat might not need a real box to cozy up in a small space.

In an interview with Catzio, Smith gave a bit of much-appreciated expert insight into the mind and concealment behavior of one of the world’s most cherished pets. Keep reading to learn why cats love boxes so much and for insights on their attraction to imaginary squares.

Why Do Cats Sit in Boxes? (Real or Fake)

Why do cats love boxes so much? It turns out, the tendency to squeeze into small spaces is not unique to the domesticated cat. Even big cats find comfort in itty-bitty hideaways. According to past research, concealing themselves in this way helps cats to manage their cortisol levels.

Cortisol is a hormone produced by the adrenal glands and plays a prominent role in cats’ natural stress response. It’s often used as a marker for monitoring stress levels in reaction to situations such as:

  • Excessive or prolonged hunger
  • Restraint (e.g., being held for extended periods or contained in a carrier)
  • Transportation (e.g., moved from place to place in a clinic or during travel)

When the cat is stressed, its cortisol concentrations rise. In some cases, they can get too high, even when the hormonal fluctuation is unwarranted. In these cases, the cat may develop Cushing’s disease (although it’s rarer in cats than in dogs), among other complications.

To mitigate these risks, cats seek a little me-time by skulking away to their hiding boxes. In 1993, Dr. Kathy Carlstead and colleagues noted that this behavior was negatively correlated with cortisol levels. In other words, hiding in compact spaces noticeably brought down their stress levels.

The scientists ultimately concluded that a cat’s interest in small, private spaces is vital. They state, “hiding is an important behavior for regulating [the hypothalamic-pituitary-adrenal] axis caused by an unpredictable environment.” Interestingly, an intangible box might just offer cats the same level of solace.

The “Cat Square” Phenomenon

In 2017, Gabriella E. Smith was scrolling through Twitter when she came across the hashtag, “#CatSquare.” Cat owners worldwide were curiously entertaining themselves and their cats using tape, the floors in their home, and a bit of imagination.

The casual observers found that, even if they made the shape of a box on the floor—instead of emptying a real cardboard box—the cats would nestle themselves inside the taped borders. The unofficial social media experiment was inspired by the long-lived phrase, often applied to cats, “if I fits, I sits.”

This refers to cats’ habit of concealing themselves in an enclosed space to lower their stress levels or merely make themselves comfortable, away from the prying eyes of other animals or human housemates. Most cats do this when their humans open up a cardboard box and leave it empty for the taking.

Cats will usually claim the space as their own, whether for play or relaxation. Many have gone so far as to make entire box castles for their little fur-babies.

Yet, few people know that the cat’s attraction to small, enclosed spaces has been passed down for millennia. And even fewer people know that the behavior applies to intangible objects, too. 

An example of the Kanisza square illusion.

How the “Kanizsa Square” Study Came About

After perusing through the amusing #CatSquare tweets, Smith reached out to Dr. Sarah-Elizabeth Byosiere, a professor in Hunter College’s Animal Behavior and Conservation Program, Department of Psychology. 

She felt an inkling of inspiration after seeing her roommate’s cat back at home and wondered, “Is there such a thing as an illusory square?” This idea arose from the famed Kanizsa triangle illusion, a sort of optical illusion that leads the human eye to see a triangle where only some non-connecting contours are present. 

This is made up of three Pacman shapes, all arranged at three points and turned inward with the apex of the V-shaped mouths aligned to suggest a triangle shape in the center. 

To make a square shape, the Pacman shapes are adjusted to four points, aligned to suggest a square in the middle instead. In Smith’s study, a control option was included, which featured the Pacman shapes facing outward in the same square arrangement.

Since the brain sees an incomplete shape, it essentially “fills in” the lines to make sense of the broken outline.

It’s common knowledge that cats’ tend to “sit on things on the floor,” as Smith put it. So, she wondered if they’d replicate that very behavior, proudly on display in the 2017 viral hashtag. 

But this was not the only inspiration. Smith and her colleagues’ study was based, in part, on a 1988 study that revealed that cats can indeed see subjective contours. The find further strengthened the project’s foundation, ultimately inspiring the Cat Square citizen science study, powered by Hunter College’s Thinking Dog Center and directed by Dr. Byosiere. They and Philippe A. Chouinard teamed up to invite homebound cat owners to help out with the study. Although, to ensure objectivity, the cat owners were unaware of the study objectives at the time. 

Boxes remind cats of feeling safe inside the protection of a den or other such enclosed spaces, helping to calm their stress.

Cats Say “‘I Fits’ in an Imaginary Box” 

Since people were so bored in quarantine, circumstances were perfect for a study setup that catered to cats’ comforts and behavior. 

“Cats behave most naturally and organically when they’re in familiar settings, and you can kind of think of it in the same way as humans when we’re going to a hospital, for example…” Smith said, explaining the team’s citizen science approach. “You act a little bit differently. You’re out of your comfort zone.” 

With the cats nice and comfy, the researchers were sure to get the behavior they hoped for. Owners voluntarily completed a preliminary survey via social media and signed up for the study via the project’s website. Of the 561 initial enrollments, 30 cats finished the entire experiment, and nine chose to sit in either the Kanizsa square or a full square shape outlined on the floor. 

Participants used common household items to make the shapes:

  • A printer with black ink
  • Printer paper
  • Scissors
  • Tape
  • Ruler

Each square, both real and “illusory,” was made to the same specifications: 20.32 cm x 20.32 cm (8 in x 8 in). They were designed to allow the cat to comfortably sit or stand inside with all four limbs naturally positioned—but not sprawled. In the end, the owners’ recordings showed that the cats chose the Kanizsa square and square shape more often than the control. 

These results demonstrated that cats are, in fact, susceptible to the illusory square. The results reveal a more “ecologically relevant paradigm” than the flagship 1988 investigation. 

“What this informs us is that they likely underwent similar evolution on their vision properties and their processes. It’s likely that they perceive contours different in luminance as humans do and the Kanizsa illusion kind of hijacked this ability to see contours based on luminance, and our brain guesses what is in the negative space,” Smith explained. 

“Our brain is assuming that the line continues. But the cat’s eye and brain perceives that the way humans’ do as well. So, some sort of shared, visual evolution, in that sense.” 

Would Wild Cats Sit in Imaginary Boxes?

Although this is completely normal behavior, you won’t see this response to imaginary boxes in wild cats as often. This is because they haven’t been exposed to human structures like domestic cats. 

To explain this, Smith referred to the Müller-Lyer illusion. The concept states that humans who grew up with different types of infrastructure perceive convex and concave lines differently. Similarly, cats that did not grow up around human infrastructure would be less susceptible to the illusion. 

An example of the Muller-Lyer illusion that Gabriella Smith, M.A. believes is functionally akin (for humans) to the Kanisza square illusion in cats.

By Franz Müller-Lyer - MathWorld - Müller-Lyer IllusionMüller-Lyer, FC (1889). 

Smith wants to explore these differences further. She said, “[I]t’s likely that they are also susceptible to [the Kanizsa square illusion] because it’s such a primordial visual phenomenon to see these types of contours. However, whether or not they…sit within contours and complete the Kanizsa would be an interesting question.” 

Generally, cats like boxes and enclosed spaces because it’s a shared ancestral trait. Even big cats have been known to sit in large cardboard boxes, such as old refrigerator packaging, in zoos. Still, the degree to which this stress-reducing concealment behavior likely varies per environment. But whether wild or domestic, this study further informs pet lovers how to keep their cats comfortable and happy. 

“If I Fits, I Sits” in Imaginary Boxes, Too 

The phrase “if I fits, I sits,” has long been shared in the cat community as a silly, affectionate reference to cats’ tendency to squeeze themselves into empty boxes and other small spaces that otherwise seem uncomfortable. 

Smith and colleagues’ study shows that this isn’t just some funny behavior. Instead, it has deep roots in felines’ evolutionary development. Further, the habit doesn’t only apply to physical objects, but to 2D or somewhat “imagined” hiding spaces, too. 

You can try your version of this citizen science experiment at home and learn more about cat behavior by tuning in to future expert chats and cat care guides with Catzio.


About the Author

My name is Jazmin "Sunny" Murphy, and I am a science communicator and web content writer. Since 2015, I've been producing scientific content that is written in plain English. My love for life science has influenced my professional and academic aspirations since I was a kid. I hold a Bachelor of Science in Zoology and 21 units of a Master's education in Environmental Policy & Management (concentration: Fish and Wildlife Management). You can learn more about me and my science writing and reporting work at my website, Black Flower Writing Services.

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