I noticed her preference because if I lie on my left-hand side, she is a very happy little spoon and uses my arm as a pillow.
If I lie on my right-hand side, kitty is confused. She will take extra preparatory rotations hoping that one more turn will be enough for the problematic situation to resolve. After some hard stares, maybe an annoyed huff, she will reluctantly curl-up as a face-to-face non-spoon.
My boy Henry will always choose my right side, tucking under my arm and his head on my chest. Which is him in a "leftward" position then.
He'll work out some kind of arrangement if I'm laying on my left side and he can't lay on his left, but if I'm lying on my back it's always to the right.
It makes you wonder about cat-person compatibility based on the person's preference for how to lie down and the cat's preference.
> My boy Henry will always choose my right side, tucking under my arm and his head on my chest. Which is him in a "leftward" position then.
OK, but what does your cat do?
That could be habit if she got used to one side rather than brain asymetry
All the cats I’ve had have a preferential side to sitting on the lap or being carried around. Trying to do it the other way the cat would either fuss and reorient or be so awkward and clumsy in the wrong orientation, akin to trying to use ones non dominant hand.
I should take some data. I've got enough cats to border crazy-cat-lady territory. I had the impression that they sleep in random positions -- basically, whatever shape they were in when the urge to nap came upon them.
I'll keep an eye on them and see if they have a preference that I'd missed. It won't be all that useful -- if nothing else, the specific preferred sleeping places of my house could have more to do with my layout than any underlying mechanism in the cat. But I'd kinda like to know if there has been something staring me in the face all this time and I just didn't put it together.
I resemble this remark. My wife and I run a feral/stray cat rescue, and anecdotally, this seems to be true, with a few caveats. In particular, the ferals tend to sleep with their backs to a wall, which overrides the left/right preference, the strays not so much.
I feel this publication could have used many more figures
I agree, obviously purely for the scientific value of the sleeping cat pictures of course..
i want the list of all 408 videos to verify the data and reproduce the results.
The list of links is in the Excel file in the attachments, so it should be reproducible.
thanks. i opened the pdf to look for the list instead of scrolling down. the pdf mentions two supplemental tables but doesn't say that those are the videos.
"Hello Ma'am, we're from the government. We're here for your cat, the one in the YouTube video. We need it to attempt to reproduce scientific research."
>To address this question, we analyzed 408 publicly available YouTube videos featuring a single cat in a clearly visible sleeping position while lying on one side, with an uninterrupted sleep duration of at least 10 seconds and full-body visibility from head to hind legs.
408 videos, showing bias towards leftward pose. They claim to have removed the mirrored videos from their samples.
YouTube videos of sleeping cats could have a left-leaning bias!
I wonder how you’d structure a proper study on this. Probably obtain a random selection of cat owners (slaves?) first.
I don’t know how random their selection was but another 2020 study on cat slow blinking that popped up on HN [1], they recruited cat “owners”. Given how militant cat “owners” can be, it wouldn’t be too hard to come up with a few hundred/thousand candidates from which to do patient selection. Just sending a DM to the cats or eyebleach subreddit mods would probably get an enterprising researcher a pinned post too.
Though his dataset is only a single cat he fails to reject the null hypothesis. But you can use the included graphics to plot the chirality of your own pet.
With my dog, the only thing I've noticed is that no matter which chirality he initially choses, he seems to need to switch it up after a while.
The author declared no competing interests, but I bet they are a certified cat lover and therefore biased
They're secretly funded by Big Cat.
They literally got paid to watch cat videos on the Internet.
Yes, that feels like some sort of event horizon, doesn’t it? If you hook the humans up to a source of power it becomes self-sustaining … for the cats.
Humans domesticated dogs, cattle, chickens, and scores of other animals.
Cats domesticated humans.
Did they check if the outcome is different on the southern hemisphere?
I prefer chirality for cats, they sleep either clockwise, counterclockwise, or possibly corkscrew.
In humans, sleeping on the left side is said to be beneficial for heartburn: https://www.health.harvard.edu/diseases-and-conditions/whats... I wonder if similar digestive benefits might be at play in cats, instead of or in addition to the paper's proposed explanation.
I think this is the opposite for lions? I'm only going by the fact that the Buddha is shown sleeping on his right side all of the time and that this is called the lion pose (not the same as the yoga lion pose). He slept on his right side in the same way male lions sleep on their right side.
(I first learned this because I was researching why when I meditated on my right side I would sometimes have hallucinogenic visions, but not on my left side - it was a surprise to come across this fact about the Buddha)
This is hilarious. While I work, one of my cats loves to share my desk chair and sleep between me and the backrest (forcing me to sit closer to the front edge). I've noticed she favors lying on her left flank there, and she is, in fact, sleeping behind me like this right now.
(Anecdotal, but +1.)
On the other hand, she's one of a bonded pair and I'll sometimes see her and her sister sleeping curled next to each other with more varied chirality. Maybe a trusted friend outweighs this effect?
That does fit with the hypothesis of the paper.
This is objectively the best paper of 2025 so far, according to the metric of number of adorable kitties depicted.
My cat does the same thing. Whenever I lie on my side, they slowly roll over to snuggle against the same side every time. If I face the "wrong" way, they fidget and squirm for a while until they settle in.
Reading this study made me realize that cats are actually very good at finding balance.
Meanwhile my parents keep sending me pictures of our cat sleeping belly up. How does he fit in this model?
Wow. Is this really a Cell article? Congrats to the authors.
Publishing in cell gets you a tenure track.
No, it’s a Current Biology article, a good journal from the Cell Press family of journals, but not quite Cell.
Cell Current Biology, not the main journal Cell
I have an ambisleptous cat, who regularly changes positions.
Am I crazy or are the cats pictured under the graph swapped? The cat under the "leftward" bar is curled the right and the cat under the "rightward" bar is curled to the left. Did they just decide that egocentrism in directions doesn't apply to cats?
They say "thus, on average, about two-thirds of cats preferred to sleep on the left side of their body with their left shoulder down", and their image for leftward lateral bias shows this. So I guess leftward means "lying on their left side", not "curling left".
But, they suggest this is because "Upon awakening, a leftward sleeping position would provide a fast left visual field view of objects", which seems suspect. When my cats sleep on their left, it's their left eye that's obscured by their paw, and their right eye that has a better field of view!
They say 'leftward sleeping position would provide a fast left visual field', while showing a cat sleeping on its left side, with its right eye having the best view (left eye with a bad view).
Clearly, there is a contradiction. What's mystifying is that the authors seemingly spent lots of time on this exact directionality concept, yet put this contradiction in.
The way I understand it, they say that animals react better to danger coming from the left side, because the left visual field (of both eyes) is processed by the right hemisphere, which is dominant for threat processing and spatial attention. So, for the cat sleeping on the left side the danger will probably come from the left side of its visual field, while for cat sleeping on the right side it would come from the right side of the visual field. Therefore, sleeping on the left side is better, because the cat will react faster to something coming towards it.
Look at this picture to see how the image from both eyes is processed:
(this is for human visual system, but it's the same for a cat I guess?)
The important thing is not the left/right eye, but the left/right side of both eyes.
That clears it up immensely, appreciate it.
Maybe they never intended for a broad audience, but the paper would be way more accessible if they had included a description like you have here. It was a frustrating read about a well-liked subject, I'm sure I'm not the only one that felt that way.
Not a biologist, but my understanding is that the temporal part of the right eye (the part of the right eye closest to the temple and furthest from the nose) is responsible for processing the inner part of the left visual field, and is directly connected to the right hemisphere (no cross-over required).
As mentioned before, this study is clearly funded by Big Cat to distract and confuse Big Mouse.
That's what Big Dog, Big Coyote, Big Racoon, and Big Wolf want you to focus on Big Mouse.
I came here to say the same thing. I’ve seen this multiple times today in several places and thought exactly that. Maybe they should have said clockwise (starting at the head) or counterclockwise?
They defined the terms in the article, as leftward is lying on their left side, left shoulder down.
Ahh thanks. I see it in the article now. This why I’m not a scientist!
> we analyzed 408 publicly available YouTube videos
Does YouTube provide a way to search and download videos for such research purposes? Or does one have to use some tool that works around YouTube’s mechanisms that prevent downloading?
yt-dlp easily downloads everything/anything from youtube.
I’d not encountered that term before. I’d always called it spatchcocking.
Oh my! Do not google that if you're a vegetarian, but do if you're a cat!
Step 1: Learning to smoke meats.
Step 2 (Optional and not recommended): Become snooty about how to prepare your poultry for being smoked.
>crossing his front paws with aristocratic grace.
Which paw on top!? Clearly of significant scientific interest.
I really like the vibes of this paper, very short, and centered around a very household topic. Sounds very inviting to junior researchers to start contributing about literally anything that they are familiar with and arouses a deep curiosity.
Wait till I tell my daughter that someone's job is watching cat videos on the internet for science!
This matches my kitty.
I noticed her preference because if I lie on my left-hand side, she is a very happy little spoon and uses my arm as a pillow.
If I lie on my right-hand side, kitty is confused. She will take extra preparatory rotations hoping that one more turn will be enough for the problematic situation to resolve. After some hard stares, maybe an annoyed huff, she will reluctantly curl-up as a face-to-face non-spoon.
My boy Henry will always choose my right side, tucking under my arm and his head on my chest. Which is him in a "leftward" position then.
He'll work out some kind of arrangement if I'm laying on my left side and he can't lay on his left, but if I'm lying on my back it's always to the right.
It makes you wonder about cat-person compatibility based on the person's preference for how to lie down and the cat's preference.
> My boy Henry will always choose my right side, tucking under my arm and his head on my chest. Which is him in a "leftward" position then.
OK, but what does your cat do?
That could be habit if she got used to one side rather than brain asymetry
All the cats I’ve had have a preferential side to sitting on the lap or being carried around. Trying to do it the other way the cat would either fuss and reorient or be so awkward and clumsy in the wrong orientation, akin to trying to use ones non dominant hand.
I should take some data. I've got enough cats to border crazy-cat-lady territory. I had the impression that they sleep in random positions -- basically, whatever shape they were in when the urge to nap came upon them.
I'll keep an eye on them and see if they have a preference that I'd missed. It won't be all that useful -- if nothing else, the specific preferred sleeping places of my house could have more to do with my layout than any underlying mechanism in the cat. But I'd kinda like to know if there has been something staring me in the face all this time and I just didn't put it together.
I resemble this remark. My wife and I run a feral/stray cat rescue, and anecdotally, this seems to be true, with a few caveats. In particular, the ferals tend to sleep with their backs to a wall, which overrides the left/right preference, the strays not so much.
I feel this publication could have used many more figures
I agree, obviously purely for the scientific value of the sleeping cat pictures of course..
i want the list of all 408 videos to verify the data and reproduce the results.
The list of links is in the Excel file in the attachments, so it should be reproducible.
thanks. i opened the pdf to look for the list instead of scrolling down. the pdf mentions two supplemental tables but doesn't say that those are the videos.
"Hello Ma'am, we're from the government. We're here for your cat, the one in the YouTube video. We need it to attempt to reproduce scientific research."
>To address this question, we analyzed 408 publicly available YouTube videos featuring a single cat in a clearly visible sleeping position while lying on one side, with an uninterrupted sleep duration of at least 10 seconds and full-body visibility from head to hind legs.
408 videos, showing bias towards leftward pose. They claim to have removed the mirrored videos from their samples.
YouTube videos of sleeping cats could have a left-leaning bias!
I wonder how you’d structure a proper study on this. Probably obtain a random selection of cat owners (slaves?) first.
I don’t know how random their selection was but another 2020 study on cat slow blinking that popped up on HN [1], they recruited cat “owners”. Given how militant cat “owners” can be, it wouldn’t be too hard to come up with a few hundred/thousand candidates from which to do patient selection. Just sending a DM to the cats or eyebleach subreddit mods would probably get an enterprising researcher a pinned post too.
[1] https://news.ycombinator.com/item?id=36132265
I prefer the paper on cat chirality:
https://blog.dimview.org/math/2017/07/28/cat-chirality.html
Though his dataset is only a single cat he fails to reject the null hypothesis. But you can use the included graphics to plot the chirality of your own pet.
With my dog, the only thing I've noticed is that no matter which chirality he initially choses, he seems to need to switch it up after a while.
The author declared no competing interests, but I bet they are a certified cat lover and therefore biased
They're secretly funded by Big Cat.
They literally got paid to watch cat videos on the Internet.
Yes, that feels like some sort of event horizon, doesn’t it? If you hook the humans up to a source of power it becomes self-sustaining … for the cats.
Humans domesticated dogs, cattle, chickens, and scores of other animals.
Cats domesticated humans.
Did they check if the outcome is different on the southern hemisphere?
I prefer chirality for cats, they sleep either clockwise, counterclockwise, or possibly corkscrew.
In humans, sleeping on the left side is said to be beneficial for heartburn: https://www.health.harvard.edu/diseases-and-conditions/whats... I wonder if similar digestive benefits might be at play in cats, instead of or in addition to the paper's proposed explanation.
I think this is the opposite for lions? I'm only going by the fact that the Buddha is shown sleeping on his right side all of the time and that this is called the lion pose (not the same as the yoga lion pose). He slept on his right side in the same way male lions sleep on their right side.
(I first learned this because I was researching why when I meditated on my right side I would sometimes have hallucinogenic visions, but not on my left side - it was a surprise to come across this fact about the Buddha)
This is hilarious. While I work, one of my cats loves to share my desk chair and sleep between me and the backrest (forcing me to sit closer to the front edge). I've noticed she favors lying on her left flank there, and she is, in fact, sleeping behind me like this right now.
(Anecdotal, but +1.)
On the other hand, she's one of a bonded pair and I'll sometimes see her and her sister sleeping curled next to each other with more varied chirality. Maybe a trusted friend outweighs this effect?
That does fit with the hypothesis of the paper.
This is objectively the best paper of 2025 so far, according to the metric of number of adorable kitties depicted.
My cat does the same thing. Whenever I lie on my side, they slowly roll over to snuggle against the same side every time. If I face the "wrong" way, they fidget and squirm for a while until they settle in.
Reading this study made me realize that cats are actually very good at finding balance.
Meanwhile my parents keep sending me pictures of our cat sleeping belly up. How does he fit in this model?
Wow. Is this really a Cell article? Congrats to the authors.
Publishing in cell gets you a tenure track.
No, it’s a Current Biology article, a good journal from the Cell Press family of journals, but not quite Cell.
Cell Current Biology, not the main journal Cell
I have an ambisleptous cat, who regularly changes positions.
Am I crazy or are the cats pictured under the graph swapped? The cat under the "leftward" bar is curled the right and the cat under the "rightward" bar is curled to the left. Did they just decide that egocentrism in directions doesn't apply to cats?
They say "thus, on average, about two-thirds of cats preferred to sleep on the left side of their body with their left shoulder down", and their image for leftward lateral bias shows this. So I guess leftward means "lying on their left side", not "curling left".
But, they suggest this is because "Upon awakening, a leftward sleeping position would provide a fast left visual field view of objects", which seems suspect. When my cats sleep on their left, it's their left eye that's obscured by their paw, and their right eye that has a better field of view!
They say 'leftward sleeping position would provide a fast left visual field', while showing a cat sleeping on its left side, with its right eye having the best view (left eye with a bad view).
Clearly, there is a contradiction. What's mystifying is that the authors seemingly spent lots of time on this exact directionality concept, yet put this contradiction in.
The way I understand it, they say that animals react better to danger coming from the left side, because the left visual field (of both eyes) is processed by the right hemisphere, which is dominant for threat processing and spatial attention. So, for the cat sleeping on the left side the danger will probably come from the left side of its visual field, while for cat sleeping on the right side it would come from the right side of the visual field. Therefore, sleeping on the left side is better, because the cat will react faster to something coming towards it.
Look at this picture to see how the image from both eyes is processed:
https://en.wikipedia.org/wiki/Visual_system#/media/File:Huma...
(this is for human visual system, but it's the same for a cat I guess?)
The important thing is not the left/right eye, but the left/right side of both eyes.
That clears it up immensely, appreciate it.
Maybe they never intended for a broad audience, but the paper would be way more accessible if they had included a description like you have here. It was a frustrating read about a well-liked subject, I'm sure I'm not the only one that felt that way.
Not a biologist, but my understanding is that the temporal part of the right eye (the part of the right eye closest to the temple and furthest from the nose) is responsible for processing the inner part of the left visual field, and is directly connected to the right hemisphere (no cross-over required).
As mentioned before, this study is clearly funded by Big Cat to distract and confuse Big Mouse.
That's what Big Dog, Big Coyote, Big Racoon, and Big Wolf want you to focus on Big Mouse.
I came here to say the same thing. I’ve seen this multiple times today in several places and thought exactly that. Maybe they should have said clockwise (starting at the head) or counterclockwise?
They defined the terms in the article, as leftward is lying on their left side, left shoulder down.
Ahh thanks. I see it in the article now. This why I’m not a scientist!
> we analyzed 408 publicly available YouTube videos
Does YouTube provide a way to search and download videos for such research purposes? Or does one have to use some tool that works around YouTube’s mechanisms that prevent downloading?
yt-dlp easily downloads everything/anything from youtube.
Ig Nobel Prize contender here.
Cleaned up url: https://www.cell.com/current-biology/fulltext/S0960-9822(25)...
My cat Emacs's signature move is the unlaterilized sploot, and I recently caught him sleeping on his back in an unlaterilized upside-down sploot!
https://en.wikipedia.org/wiki/Splooting
My tuxedo cat Napoleon is much more dignified, presenting a distinguished catloaf, while crossing his front paws with aristocratic grace.
https://en.wikipedia.org/wiki/Cats_and_the_Internet#Catloaf
I’d not encountered that term before. I’d always called it spatchcocking.
Oh my! Do not google that if you're a vegetarian, but do if you're a cat!
Step 1: Learning to smoke meats.
Step 2 (Optional and not recommended): Become snooty about how to prepare your poultry for being smoked.
>crossing his front paws with aristocratic grace.
Which paw on top!? Clearly of significant scientific interest.
I really like the vibes of this paper, very short, and centered around a very household topic. Sounds very inviting to junior researchers to start contributing about literally anything that they are familiar with and arouses a deep curiosity.
Wait till I tell my daughter that someone's job is watching cat videos on the internet for science!
Previously submitted: https://news.ycombinator.com/item?id=44371307