Study Finds Two-Thirds of Domestic Cats Prefer Left-Side Sleep Position

A recent study conducted by researchers from Ruhr-University Bochum, the University of Prince Edward Island, Ankara University, and the University of Bari Aldo Moro reveals that approximately two-thirds of domestic cats (Felis silvestris catus) exhibit a preference for sleeping on their left side. This behavior, as outlined in the research published in the journal Current Biology on June 24, 2025, suggests an evolutionary adaptation linked to visual and threat perception.

The study analyzed 408 publicly available YouTube videos featuring individual cats in clearly visible sleeping positions. Researchers included videos that displayed uninterrupted sleep durations of at least ten seconds, ensuring full-body visibility. The findings were notable, with 266 cats (65.1%) observed sleeping on their left side, while only 142 cats (34.8%) preferred the right side.

Professor Onur Güntürkün from Ruhr-University Bochum, a co-author of the study, emphasized the significance of this leftward bias in sleeping position. “Sleep is one of the most vulnerable states for an animal, as anti-predator vigilance is drastically reduced, especially in deep sleeping phases,” he stated. In his view, domestic cats, which balance roles as both predators and prey, may have evolved this behavior to enhance their survival.

The research posits that cats sleeping on their left side may be better positioned to perceive threats from their left visual field, which is processed by the right hemisphere of the brain—an area specialized for spatial awareness and threat detection. “Cats that sleep on their left side perceive their surroundings upon awakening with their left visual field, which directly engages their right brain hemisphere,” the researchers explained.

This lateralized sleeping behavior is thought to be a survival strategy, allowing cats to maximize their awareness of potential dangers while in a vulnerable state. The study further highlights the importance of elevated sleeping positions for cats, as these spots provide greater visibility of threats and concealment from predators.

This research adds to the growing body of literature on animal behavior and cognition, suggesting that even seemingly simple behaviors, such as sleeping positions, can have complex evolutionary underpinnings. The implications of the study extend beyond feline behavior, offering insights into the broader field of animal cognition and the evolutionary strategies that govern predator-prey interactions.

Future research may explore similar lateralized behaviors in other species, potentially broadening our understanding of evolutionary adaptations in the animal kingdom. The findings of this study not only enrich our knowledge of domestic cats but also underscore the intricate relationship between behavior, environment, and survival strategies in animals.