17-07-2025
Does your cat prefer to sleep on their left side? Scientists have investigated why...
Why do I snore? What possible purpose does it serve?
Our ancient hominid ancestors can't have snored; the noise would have drawn predators, such as leopards, to the sleeper. Natural selection would soon have eliminated such a tendency.
Cats don't snore but they have other sleeping foibles. Alanna, our pussy, slumbers through much of the day. But she won't curl up just anywhere; she commandeers the highest available location before nodding off. That would have made good survival sense to her wild forebears. An approaching predator is easier to spot from above and is less likely to notice the sleeper. Enemies, apart from eagles, having to attack uphill from below, would be at a tactical disadvantage.
But Alanna has another quirk; she always sleeps lying on her left side.
I used to think that such traits were peculiar to her but, according to a paper just published in Current Biology, they aren't. Every domestic cat, it seems, has a preferred sleeping position and each one always chooses to lie on a particular side of the body.
Could this 'lateral bias' be down to 'handedness'? About one in ten people is left-handed. It used be thought that ciotógs were more talented and creative than the rest of the common herd. The most famous lefties were Leonardo da Vinci and Vincent van Gogh. Barack Obama and Bill Gates both write with the left hand. However, researchers at Cornell University found no evidence that 'kicking with the left foot' meant that you were more gifted.
'Pawedness', the animal equivalent of handedness, is found in many, perhaps all, vertebrates:
Parrots prefer to hold food items in one claw rather than the other.
Pregnant cows sleep more often lying on their left side than on the right, whereas non-pregnant ones show no side preference.
Amphibians and reptiles have similar biases.
Whether fish exhibit pawedness, is uncertain.
Nor is the choice of side written in stone; most dogs, for example, are right-pawed, although bitches and pups, according to one study, are more likely to be lefties.
Lateral bias in sleeping positions of domestic cats: About two-thirds of cats prefer to sleep on their left side. Pictures of cats from unsplash: left cat courtesy of Noah Dustin von Weissenfluh (@noah_dustin), right cat courtesy of Gleb Kuzmenko (@badfantasy)
Researchers, led by Sevim Isparta of Italy's Bari Aldo Moro University, have studied handedness in domestic cats. Examining 408 Youtube videos of sleeping pussies, they found that 65% of them sleep on their left side, while 35% chose the right.
There is a division of labour between the two sides of the brain. Each side specialises in particular tasks. The right hemisphere, say the researchers, 'is dominant for threat processing and, in most species, animals react faster when a predator is approaching from the left side'. It analyses spatial information while the right amygdala responds to dangers and threats.
If a cat, sleeping on its left side, is awakened by the approach of a predator, the threat would be detected in the cat's left visual field. The left side of the brain controls the right side of the body, so left visual information is processed in the right hemisphere. Sleeping on the left side, therefore, may have evolved as a 'fight or flight' mechanism to help the cat respond more quickly to danger and hunt for prey more efficiently.
Left-oriented sleeper Alanna agrees!
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