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Physics test suggests cats understand gravity, Japanese researchers say

(Saho Takagi/Kyoto University)
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Of all the furry ambush predators on the planet, domestic house cats — some 600 million of them — are among the most numerous. Their ancient evolutionary history does not always feel so ancient, as anyone who has lobbed a catnip mouse at a tabby or wiggled a defenseless ankle near a kitten can attest.

With their hunting instincts comes superior night vision, letting cats navigate shadowy environments that would send most humans stumbling. What is perhaps less well known, but no less impressive, is their listening ability. Cats are creatures of sound, with swiveling ears that put human organs to shame. (The hearing range for cats is estimated to be between 55 to 79,000 hertz, versus about 20 to roughly 14,000 hertz for adult humans.) Cats readily predict the location of entities they can hear but cannot see, Japanese researchers concluded in a 2015 paper.

And in a new report, published Tuesday in the journal Animal Cognition, the same group of scientists argues that a hearing test reveals cats comprehend gravity, or something like it. “Our study is the first demonstration that cats seem to grasp the laws of physics,” Kyoto University’s Saho Takagi, an author of the paper, wrote in an email to The Washington Post. Based on a small sample of 30 cats, the research suggests the creatures have an inkling of physical cause-and-effect.

Watch: Everything you ever wanted to know about cat behavior, in just 5 minutes

To assess these whiskered Isaac Newtons, Takagi and her colleagues constructed a magnetized ball-dropping container: Two plastic compartments with an electromagnet sandwiched in the middle. Inside, the cup held an object — three iron balls clumped together. A flick of a switch turned the electromagnet on, so that even when the cup was flipped upside down the balls remained stuck to an inner steel plate. Switch the magnet off, and the iron cluster plunked out.

Using the custom container, the researchers constructed four different scenarios, presented to 22 felines in Japanese cat cafes plus eight pet cats. (When asked why scientists would want to experiment on cats in cafes, Takagi noted that many house cats are too shy to study.  “Almost all cats living in cat cafes are friendly toward strangers,” she pointed out.) As the cats watched — or ignored the researchers — scientists shook the container like a Yahtzee cup and videotaped the animals’ reactions.

D.C.’s cat cafe is so successful that it’s opening a second cafe in Los Angeles

Two of the trials had “expected” outcomes. If a scientist shook the container while the magnet was off, the cup made a rattling sound; when the cup was flipped over, the iron ball dropped out. In the other expected scenario, when the magnet was always on, the container produced neither a sound when shook and nor a ball when flipped. The goal was, simply, no surprises.

The other two scenarios were what the scientists describe as “expectancy violation procedure” — which is to say that the shake-drop process did not make auditory sense. In the first incongruous setting, the scientist shook the cup with the electromagnet on, so the iron ball could not move or make a sound. But then the researcher turned the magnet off and flipped the cup, so out spat a ball. (Weird scenario one: No sound, but a ball.) Or, she rattled the container — switch off — but then magnetized the plate so nothing dropped out. (Weird scenario two: Sound, but no ball.)

When reviewing the tapes of the experiments, the researchers concluded that cats spent significantly more time looking at the weird scenarios than the ones that made sense. If you accept that prolonged cat stares indicate violated feline expectations, then it is evidence, the scientists say, that cats inferred the existence of a ball using a physical cause-and-effect rule.

In other words, the scientists believe that when a cat hears a rattling cup, the animal infers the cup must have something in it. And, should a ball drop out of the container when it’s turned over — thanks to physics — that, to a cat, is normal. But if there is a glitch in the processes, like the lack of sound or lack of ball, the cat reacts with a longer gaze. The feline expectations have been violated: Whether the cats are curious or perplexed the scientists do not say, but they argue that anticipating a ball that never drops (or prolonged inspection of a ball that should not exist) is a limited grasp of physics.

“This study may be viewed as evidence for cats’ having a rudimentary understanding of gravity,” they write.

There are, however, certain caveats — namely, there is a paucity of behavior research with which to compare this report. “We still have a long way to go until we have an inclusive body of research on cat cognition,” a trio of Oregon State University scientists wrote in a 2015 review of feline behavioral science. “Many questions are still largely unexplored.”

University of Bristol’s John Bradshaw, an expert on domestic pets and author of the book “Cat Sense,” called the study “seriously flawed” in an email to The Washington Post. Where the Japanese researchers saw feline comprehension of cause-and-effect, Bradshaw saw cats simply paying attention to the sounds of rattling and falling balls. Bradshaw does not doubt that cats may have expectations between what they see and hear — but this paper does not convince him.

“This idea is entirely plausible, given the kind of hunters cats are,” he said. “I just don’t think that this experiment provides conclusive evidence one way or another, because the second stimulus had both auditory and visual elements.”

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Moreover, cats are tricky to study, at least when compared with the more sociable dogs. Takagi and her colleagues excluded 15 cats from the study thanks to experimenter error — or due to fear or total disinterest on the part of the cats. (The idea that the same expressions of “expectancy violation” hold true across individuals in a population, too, is not without its critics.)

“Cats have a lot of abilities,” Takagi acknowledged, “that we do not understand yet.”

Still, Takagi believes that having this trait makes sense — the cat’s “natural hunting style,” she said “may favor this cognitive ability.”

This post has been updated.

After a backpacking trip in Thailand, Kanchan Singh, 24, put everything on the line to launch a cat cafe in D.C. Here are some of her four-legged friends. (Video: Sarah Parnass/The Washington Post)