— By Andru Shively — 

Octopuses: enigmatic, alienlike, highly intelligent. Biologists in Japan have now demonstrated that the cephalopods are self-aware and possess a sense of body ownership – all thanks to a tentacle made of polymers.

The research team at the University of the Ryukyus subjected six plain-body octopuses to the body transfer illusion, also known as the rubber hand illusion. In the classic scenario dating back to 1998, a person’s (hidden) real hand and a dummy positioned in its place are touched simultaneously, leading the brain to incorporate the fake hand into the body; when the fake is then touched alone, the person continues to “feel” the sensation.

In the Japanese study, a decoy arm made of soft gel was similarly placed in front of an octopus, with a real one hidden from its view. Both were stroked in sync with calipers, after which only the fake was pinched with tweezers. All six octopuses responded defensively: changing colour or posture, retracting their arms, or trying to flee. When the stroking was out of sync, or the gel limb was positioned unnaturally, the illusion was broken, with no reaction triggered.

This suggests that octopuses perceive body ownership of their arms, a sense that is “a fundamental aspect of self-consciousness”, according to the researchers. While mice and rhesus monkeys have previously been shown to fall for the same trick, this marks the first time for a non-mammal and invertebrate, suggesting a deeper evolutionary link for the construction of self.

So, it might be our cerebral differences that are the real illusion. Could you gel with such an idea?