An international team of researchers has discovered that cats prefer to sleep on their left side, which offers an evolutionary advantage. The study, published on June 23, 2025 in Current Biology, analyzed hundreds of YouTube videos and was conducted by scientists from the University of Bari Aldo Moro, Ruhr University Bochum, Medical School Hamburg and partners in Canada, Switzerland and Turkey.

Cats sleep 12 to 16 hours a day, often in elevated places to protect themselves from predators. The researchers investigated whether cats have a preferred sleeping posture and whether this is related to behavioral asymmetries. For this purpose, 408 publicly available YouTube videos were analyzed, each showing a cat sleeping on one side for at least ten seconds. Modified or mirrored material was excluded. The analysis showed that two thirds of the cats slept on their left side.

This behaviour is explained by the specialization of the cerebral hemispheres. The right hemisphere, which processes the left visual field, is specialized in spatial awareness, threat detection and rapid escape movements. Cats that sleep on their left side perceive their surroundings primarily with the left visual field when they wake up, which optimizes the processing of potential dangers. The researchers conclude that this sleeping posture is a survival strategy, as it improves the ability to react to predators or prey after waking up.

The study highlights how behavioral asymmetries can provide evolutionary advantages and provides new insights into the neurological basis of sleep behavior in cats.

Original Paper:

Lateralized sleeping positions in domestic cats: Current Biology

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