At a Glance
- Researchers have demonstrated that octopuses possess a sense of body ownership, a form of self-consciousness previously studied primarily in mammals, such as humans, monkeys, and rodents.
- Using the rubber hand illusion, scientists tricked octopuses into accepting a fake arm as their own by simultaneously stroking it and their real, hidden arm.
- When the fake arm was pinched, all six octopuses in the experiment exhibited defensive responses, such as fleeing or changing color, as if their real arm were hurt.
- This discovery suggests that a complex sense of self can evolve independently in invertebrates, which have nervous systems vastly different from those found in vertebrates.
- The findings could advance robotics and AI development, as well as improve our understanding of human neurological disorders that affect a person’s awareness of their body parts.
New research shows that octopuses, like humans, can be tricked into believing a fake arm is their own, demonstrating for the first time that an invertebrate possesses a sense of body ownership. This perception is our innate understanding that our limbs belong to us and is a key component of self-awareness. The study, published in the journal Current Biology, employed a classic experiment known as the rubber hand illusion to investigate this complex cognitive ability in a non-mammalian animal, providing new insights into the evolution of consciousness.
The experiment was led by researchers Sumire Kawashima and Yuzuru Ikeda at the University of the Ryukyus in Japan. They placed an octopus in a tank where one of its real arms was hidden from view by a partition. In its place, the octopus could see a realistic fake arm made of a soft gel. Scientists then used plastic calipers to simultaneously stroke both the hidden real arm and the visible fake one. This synchronous stroking creates a multisensory trick, which in humans is enough to fool the brain into adopting the fake hand as part of its own body.
After about 8 seconds of stroking, the researchers tested the illusion by pinching the fake arm with tweezers. In response, all six octopuses tested exhibited defensive behaviors, such as fleeing, changing color, or retracting their arms, as if their real arms had been harmed. To confirm the results, the scientists conducted control experiments in which the stroking was performed out of sync or where the fake arm’s posture did not match that of the real one. In these cases, the octopuses did not react, indicating that the illusion was dependent on synchronized visual and tactile feedback.
These findings have significant implications, suggesting that a sophisticated sense of self can evolve in animals with nervous systems vastly different from our own. “These findings in the octopus… may be an important model for studying the evolution of the sense of body ownership,” the researchers wrote. The study not only deepens our understanding of animal cognition but may also inform advancements in robotics and artificial intelligence, helping scientists better understand human neurological disorders, such as asomatognosia, where a person loses awareness of their body parts.
References
- Arnold, P. & Phys.org. (2025, July 22). The rubber hand illusion works on octopuses too. Phys.Org; Phys.org. https://phys.org/news/2025-07-rubber-illusion-octopuses.html
- Kawashima, S., & Ikeda, Y. (2025). Rubber arm illusion in octopus. Current Biology, 35(14), R702–R703. https://doi.org/10.1016/j.cub.2025.05.017
