It’s not just humans that can understand the laws of physics in a practical, everyday sense. Cats, too, have a good grasp of how the physical world works. They know, for instance, that if there’s a scratching sound coming from behind the refrigerator, then a mouse may be about to dash out. This understanding of cause and effect may be why cats are such formidable hunters.
In a newly-published paper, researchers led by Saho Takagi, of the Department of Psychology at Kyoto University, tested cats to see if they could infer future events based on something happening in front of them. In the experiment, researchers shook a cup with an object inside, which rattled. Then they turned over the cup. The experiment was rigged so that the natural order of events (object rattles, then drops out, or no rattle, and nothing dropping out) only occurred half the time. The other half, a rattling cup would produce no object, and vice versa.
The idea was to see if animals can infer the "whole picture" from partial information. "When animals perceive incomplete information, they may have to complete the remaining parts from other available clues," says Takagi. "It would be beneficial to animals’ adaptation to the environment and their survival if they could infer information based on incomplete clues."
Similar experiments done in the past on primates show that apes, and therefore humans, are a lot better at causal reasoning based on visual information than we are with auditory information. Given that we make sense of the world visually, that seems sensible. Cats, on the other hand, seem set up to process sound. They can hear sounds from 55Hz to 79kHz (the human range is 20Hz to 20kHz), and have 22 muscles just to control the ears, the independent movement of which allows fine-tuning of their hearing.
In a previous, almost identical experiment, Takagi’s team used the cup and ball trick, only without the odd non-appearing ball variation. In that experiment, the cats did indeed seem to connect the sound and the appearance of the ball, but it could have been, as Takagi writes, "that the cats simply had a visual preference for the motion accompanied by sounds."
The new experiment added the incongruent component to see if cats really did understand the link between sound and subsequent movement. "We hypothesized that if cats infer the presence (or absence) of an object inside the container upon hearing (or not hearing) rattling noises, they would be surprised at physically incongruent events and thus would look longer at the apparatus and explore around it more than in congruent conditions."
The result, as you will have guessed if you’ve ever spent time with a cat, is that they are indeed puzzled when a rattling cup fails to produce a ball (and vice versa), and spent longer exploring the apparatus when these event occurred. This fits with the hunting style of cats, which appears to be based largely on sound, and inferring the outcomes from those sounds. But the results also, says Takagi, indicated that cats are pretty good at physics.
"This study may be viewed as evidence for cats having a rudimentary understanding of gravity," he writes.
We assume that, thanks to our big brains, we are the only species capable of understanding how the world works. But more and more experiments show that we share our intuitive understanding of physical laws with other animals. It’s just that we’re a lot better at describing them, or writing blog posts about them.
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