Home experiments shed light on cats’ liquid behavior

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

Cats move fluidly around high, narrow corners, but hesitate when approaching uncomfortably short holes, reports biologist Péter Pongrácz on September 17, 2019. iCiência. The discovery suggests that cats are aware of their own body size and can form mental images of themselves.

Pongrácz, from Eötvös Loránd University in Budapest, tested dogs in a laboratory and showed that dogs are capable of self-advocacy. In this study, published in 2019 in Animal Cognitionthe dogs slowed and hesitated before passing through uncomfortably small openings, revealing that they rely on awareness of their body size to make decisions. After the experiment was over, Pongrácz thought: “What about cats?” he says.

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

With the help of colleagues, Pongrácz built a portable laboratory that he installed in the homes of 29 cat owners in Budapest. In each house, the team attached two large cardboard panels to the door frame: one with five holes of the same height but decreasing width, and another with five holes of the same width but decreasing height. One owner stood on one side of the panel while the cat and 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 instructions is a difficult task. Unlike dogs, cats are difficult to call back to a location. Once a cat slipped through the hole, the owner had to pick up their pet and hand it over to the researcher to start a new test. But some cats hated being handled and avoided their owners’ hands at all costs, says Pongrácz.

Thirty of the 38 cats finished the experiment. When faced with holes of varying heights, 22 cats hesitated to crawl through the shortest one, an analysis of the recordings revealed. When the holes varied in width, only eight cats stopped before approaching the narrowest crack. Most cats passed through narrow openings without hesitation. The team calls this strategy trial and error: Regardless of whether the cats fit or not, they tried to flow.

In the wild, this hesitancy to bend 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, it could be making itself vulnerable to potential threats. The fact that they still pause in the safety of their homes suggests that cats also rely on representations of body size, or how they imagine their body size, 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 carried out a similar experiment with bees and in 2020 published the first study to show that a flying insect was aware of the size and shape of its body. But he suspects cats may act differently depending on why a feline wants to squeeze through a hole. For example, a cat may hesitate to go through a hole while chasing a mouse to avoid injury during rapid movements. “This is something the study could have commented on or even experimented with,” says Ravi.

Despite the challenges of testing cats, Pongrácz still had a lot of fun. He has met many funny cats, but says “the funniest thing is how people behave.” Some owners thought their cats were geniuses, but these felines had a hard time with the experiment. Other owners were convinced that their cats lacked intelligence. Minutes later, the cats would complete the task with ease, shocking their owners.