Octopuses can be tricked into thinking that a fake arm is part of their body, suggesting they have a sense of body ownership similar to our own
By James Woodford
21 July 2025
Plain-body octopuses can be duped into thinking a fake arm is their own
Sumire Kawashima and Yuzuru Ikeda/the University of the Ryukyus
Just like humans, octopuses can be fooled by an illusion that makes them think a fake arm is actually theirs.
First demonstrated in the late 1990s, the rubber hand illusion involves hiding a person’s real hand and placing a fake one on a table in front of them, then stroking both simultaneously. Later, it was found that other mammals, such as mice, can also be fooled by the same trick.
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Now, Sumire Kawashima and Yuzuru Ikeda at the University of the Ryukyus in Okinawa, Japan, have discovered that octopuses are also vulnerable to the illusion.
For the study, captive plain-body octopuses were placed in an experimental tank. A fake octopus arm made of soft gel attached to an opaque partition was placed over one of the octopus’s arms, blocking its view of the real arm. Then one of the researchers used plastic callipers to stroke both the fake arm and the real arm at the same time.