Home Experiments Reveal Insights into Cats' Liquid-Like Behavior

Cats may seem solid, but they’re actually somewhat liquid — at least according to one 2017 theoretical physics paper inspired by videos of cats squeezing under doors, into tight vases and down narrow crevices. Now, one researcher has taken this idea a step further, physically testing dozens of cats to see when they act more like liquids or solids.

Cats fluidly move through tall and narrow nooks but hesitate when they approach uncomfortably short holes, biologist Péter Pongrácz reports September 17 in iScience. The finding suggests that cats are aware of their own body sizes and may form mental images of themselves.

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Pongrácz, of Eötvös Loránd University in Budapest, tested dogs in a lab and showed that dogs are capable of self-representation. In that study, published in 2019 in Animal Cognition, dogs slowed down and hesitated before walking through uncomfortably small openings, revealing that they rely on awareness of their body size to make decisions. Once the experiment was done, Pongrácz thought, “What about cats?” he says.

But cats are more difficult to test in the lab than dogs. Felines tend to be reclusive and would be stressed out in that environment, Pongrácz says. So, he brought the lab to the cats.

With help from colleagues, Pongrácz built a portable lab that they set up in the homes of 29 cat owners throughout Budapest. In each home, the team attached two large, cardboard panels to a doorframe: one with five holes of the same height but decreasing width and another with five holes of the same width but decreasing height. An owner stood on one side of the panel while the cat and the experimenter stood on the other. For each trial, the cat had to squeeze from the experimenter’s side to the owner’s side through the holes while being filmed.

Getting cats to follow directions is a tough task. Unlike dogs, cats are hard to call back to a spot. Once a cat oozed through the hole, the owner had to catch their pet and hand them over the panel to a researcher to start a new trial. But some cats hated being handled and evaded their owners’ hands at all costs, Pongrácz says.

Thirty out of 38 cats finished the experiment. When faced with holes of varying height, 22 cats hesitated to crawl through the shortest, an analysis of the recordings revealed. When the holes varied in width, only eight cats paused before approaching the narrowest cranny. Most cats squeezed through slim openings without hesitating. The team calls this strategy trial-and-error: Regardless of whether the cats fit or not, they tried to flow through.

In nature, this hesitation to hunch down and crawl through short holes may be a self-preservation strategy, Pongrácz says. If a cat squeezes through a hole without being able to see what’s on the other side, they may be making themselves vulnerable to potential threats. The fact that they still pause in the safety of their homes suggests that the cats also rely on their body size representation, or how they imagine their body sizes, to plan their approach.

Pongrácz’s experiment is simple and elegant, says Sridhar Ravi, an aerospace engineer at the University of New South Wales in Australia. Ravi performed a similar experiment with bumblebees and in 2020 published the first study to show that a flying insect was aware of its body size and form. But he suspects that cats may act differently depending on why a feline desires squeezing through a hole. For example, a cat might hesitate to trek through a hole while chasing a mouse to avoid injury during quick movements. “That is something the study could have commented on or even experimented,” Ravi says.

Despite the challenges of testing cats, Pongrácz still had a lot of fun. He met many amusing cats, but says that “the funniest things are how the people behave.” Some owners thought their cats were geniuses, only for those felines to struggle with the experiment. Other owners were convinced their cats lacked intelligence. Minutes later, the cats would easily complete the task, shocking their owners.