Most people don’t expect octopuses to fall for one of psychology’s oldest illusions. But new research shows that these famously clever invertebrates are just as susceptible to the “rubber hand illusion” as humans are.

In people, the illusion happens when a fake hand is stroked in sync with a person’s hidden real hand, tricking the brain into accepting the fake limb as its own. Researchers Sumire Kawashima and Yuzuru Ikeda from the University of the Ryukyus adapted this experiment for octopuses.

They placed each animal’s real arm behind a barrier and a silicone replica in plain view. When both arms were stroked at the same time, the octopuses reacted in ways that suggested they had adopted the fake limb as part of their body.

What this tells us about body awareness

The experiment, published in Current Biology, is the first to demonstrate this illusion in a non-vertebrate. Octopuses aren’t just mimicking responses. Their reactions to desynchronized stroking, such as twitching or recoiling, show that their nervous systems integrate visual and tactile information in a way that produces a coherent sense of self.

This is surprising for a creature with such a radically different body plan and neural architecture. Two-thirds of an octopus’s neurons are located in its arms, not its central brain. Despite this decentralized system, the octopuses in the study acted as if they perceived the fake limb as their own when sensory cues aligned.

Researchers observed behaviors like gentle exploration of the fake limb or defensive actions when it was touched, mirroring how humans sometimes flinch when their “adopted” rubber hand is threatened. In some cases, octopuses even moved in ways to protect the fake limb, a sign that they internalized it as part of their body.

Beyond the novelty, these results could reshape how we understand bodily self-awareness in animals. If octopuses experience something like body ownership, it opens up new questions about how consciousness evolves, especially in animals without spines, familiar faces, or vocal cords.

Some scientists think this could help build better underwater robots modeled after cephalopod movement. Others point to its potential for developing therapies for people who have lost limbs or experience phantom limb pain. The study even raises questions about whether other animals might be experiencing similar illusions,and whether this suggests deeper forms of selfhood across the animal kingdom.

“This tells us that body representation is not unique to vertebrates,” Kawashima said. “Even animals with completely different neural architectures can develop a representation of their body.”

The next step? Testing whether cuttlefish or squid, octopus cousins with similarly complex nervous systems, fall for the same trick.