June 26, 2025, 3:58 am | Read time: 4 minutes
Sleeping cats appear deeply relaxed, but their sleeping position might reveal more than you think. A study shows that two-thirds of all cats prefer a specific side when sleeping—and apparently not by chance. What lies behind this peculiar preference, and what does it say about our housecats’ perception?
Do cats prefer to sleep on their left or right side? What initially sounds like an individual preference might have a biological basis, as a study shows. According to this, cats often subconsciously choose a specific sleeping side.
Left or Right? How Cats Sleep Is Linked to the Opposite Brain Hemisphere
It has long been known that many animals, including cats, exhibit what are called lateralizations—a preference for one side of the body, such as when using their paws. For example, it is known that male cats are often “left-pawed.” We demonstrated this in a PETBOOK article with our own experiment with the cat Remo: Can Cats Be Left- or Right-Handed? Studies Show They Can.
This principle applies not only to movements but also to sensory perceptions and the processing of information in the brain. Such specialization can offer advantages: One hemisphere of the brain handles tasks like quick reactions to dangers, while the opposite hemisphere takes on other functions.
Particularly, the right hemisphere plays a central role in many animal species in the perception and processing of threats. It reacts more quickly to stimuli coming from the left. These are in the left visual field and are processed in the right hemisphere. Researchers wanted to know if this functional asymmetry also plays a role in cats’ sleep.
Nearly Two-Thirds of Cats Are Left-Sleepers
A total of 408 videos of house cats, which slept undisturbed in a clearly recognizable side position for at least 10 seconds, were examined. Only unedited, high-quality videos were considered. The international research team, led by Sevim Isparta (University of Bari), Sebastian Ocklenburg (Ruhr University Bochum), and Yasemin Salgirli Demirbas (University of Prince Edward Island), assessed whether the cat lay on its left or right side. The study was published in the renowned journal “Current Biology” (issue of June 23, 2025).
The analysis revealed a significant trend: 266 of the 408 cats (65.15 percent) lay on their left side. Only 142 cats (34.85 percent) slept on the right side. The difference was statistically highly significant, showing a clear left-side sleeping trend at the population level.
This means the majority of cats prefer to sleep with their left shoulder down. This position gives the left visual field—and thus the right hemisphere—a clear view of potential threats, such as from lower positions or below. Since cats prefer to sleep elevated, this posture could be an evolutionarily developed precaution to react to dangers even while asleep.
Alert Even in Sleep
The side position in cats is actually a posture in which they sleep particularly deeply. Learn more about sleep positions and what they express here: Bread, Croissant, or Pretzel? 14 Cat Sleep Positions Explained.
However, the connection discovered by the researchers could mean that these small predators want to react particularly quickly to threats even in the deepest slumber. That they remain subconsciously in a “standby mode” even in this relaxation pose provides important insights into the functional organization of the cat brain and its evolutionary development. The left-leaning sleep could be an adaptation that allows cats to quickly “activate” the reactive right hemisphere in the face of threats.
This specialization would not only be another example of the lateralization of animal behavior but could also deepen the understanding of rest behavior, attention, and responsiveness in pets. Furthermore, comparisons can be drawn to other animal species where similar mechanisms have been observed—such as in the flight response to stimuli in the left visual field. The study thus contributes to understanding how rest phases are linked to protective behavior and brain architecture.
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Further research could use the “Feline Five” personality model to explore whether right-sleepers in the cat world generally feel more secure in their environment and whether left-sleepers are generally prone to anxiety or neuroticism. A study comparing the sleep positions of feral cat colonies and purely domestic cats would also be interesting in this context. Additionally, the question of whether shelter animals generally sleep more on the left or switch to the right as they feel more secure after adoption could provide insights into the relationship between sleep position and behavior.
It would also be intriguing to investigate whether individual “paw preference” has an influence. According to the researchers, it is probably not the main factor, as it is individually different and relatively evenly distributed.
For cat owners, the study already offers a fascinating insight into the hidden logic of animal behavior. For research, the findings provide a new perspective on the interplay of brain architecture, behavior, and protective strategies during rest phases. 1