Scientists have discovered why cats sleep on their left side

There is no more touching sight than a sleeping cat. But until now, few people thought about what determines the choice of cat sleeping positions. Until a team of scientists devoted an entire study to this and found out that most cats prefer to sleep on their left side. Why - scientists also answered this question. The left-sided sleeping position in cats is an asymmetry at the population level and, possibly, represents an evolutionary advantage.

A study titled “Lateral Sleeping Postures in Domestic Cats” was recently published in the scientific journal Current Biology. The authors of the publication are researchers from the University of Bari Aldo Moro (Italy), Ruhr University Bochum (Germany), UPEI, Hamburg Medical School (Germany), Kafkas University (Turkey) and the Research Institute for Agricultural Animal Biology (Germany) – they discovered that cats that sleep 12-16 hours a day prefer to sleep on their left side. This is the case for 65% of cats.

How did the scientists know this? To answer the question of which side cats prefer, the researchers seriously analyzed 408 publicly available videos online of one cat sleeping on its side, with the uninterrupted sleep lasting at least 10 seconds, and the cat's entire body visible from head to hind legs. Two-thirds of the videos showed the cat sleeping on the left.

The reason cats sleep on their left side is not simple. According to the authors of the study, the right hemisphere of the brain, which controls the left side of the visual field in mammals, including cats, is responsible for spatial perception, processing threats, and coordinating quick movements to escape. When cats are awake, the right hemisphere of their brain allows them to directly see predators and prey. Cats that sleep on their left side have an important advantage.

"Because cats prefer to sleep in an elevated position, upon awakening they will immediately see predators or prey on the left side of their visual field, which is processed by the right half of their brain. Since the right hemisphere has developed spatial abilities and can quickly coordinate the functions of rapid escape and possibly also hunting, sleeping on the left side may provide evolutionary advantages as a survival strategy," the scientists conclude.

"65% is a statistically significant difference, which means that the tendency to sleep on one side must have some biologically sound explanation," says scientist and biologist Irina Yakutenko. "According to the authors, the left-sidedness of sleeping cats helps them minimize risks. During sleep, cats are in a very vulnerable state, so in the wild they prefer to sleep on an elevated surface: in this position, predators have a worse view of them, and the cats themselves, on the contrary, have the widest possible view when waking up. In principle, such an explanation seems logical, because brain lateralization, that is, the preferential processing of different types of information in the right or left hemisphere, is a well-described fact. And although it is not absolute, and complex behavior is processed by both hemispheres, the initial asymmetry takes place."

And yet, the expert considers this study to be rather weak. A video of a cat sleeping for 10 seconds is not enough to draw full conclusions. “It cannot be ruled out that at different stages of sleep, cats prefer different sides of the body. Since these were random cats from the Internet, the authors do not have data on the sex, age, castration, health or pregnancy of the cats. And each of these factors can significantly affect behavior, including sleeping positions. Only one video was available for each cat, but it is very possible that the preference for the left or right side is not an adaptation to sleeping in dangerous conditions, but the individual preferences of specific animals. In addition, it is not always possible to tell from the video whether the filming was done on the main or front camera.

Well, and finally, it may well be that it is not the cats that prefer to sleep on their left side, but the owners who prefer to photograph cats sleeping on their left side. In short, I would not take this work too seriously. Although any new information about cats is absolutely necessary to enrich our inner world," notes Irina Yakutenko.