Octopus and the Rubber Hand Illusion

For a long time, it was believed that the visual illusion known as the “rubber hand illusion” was limited to certain mammals like humans and mice. However, a recent study published in the journal Current Biology shows that octopus brains can be tricked in the same way, adding a new dimension to our understanding of these marine creatures.

The Rubber Hand Experiment: An Overview

The rubber hand experiment is a classic in experimental psychology, where a participant is tricked into perceiving a fake arm placed in front of them as part of their own body. The brain perceives sensory stimulation applied to the fake arm as if it were applied to their real arm, even when the real arm is hidden behind a barrier. Traditionally, it was thought that the ability to fall for such an illusion was limited to certain mammalian animals.

The Experiment on Octopuses: Methodology

Scientists began by placing an octopus in a water tank where it could relax on a soft surface resembling the seabed. They then introduced a barrier covering one of the octopus’s arms and left a visible fake arm in its place. It was crucial that the rubber arm resembled the octopus’s real arm, as the illusion does not occur if the fake arm differs in appearance from the real one.

Initially, the octopus showed no reaction when the fake arm was gently touched, but when it was grasped firmly with tongs, the octopus exhibited a defensive response. The study’s lead author, Sumire Kawashima, noted that the reaction depended on the strength of the stimulus used.

Study Results: A Better Understanding of Octopuses

The study revealed that octopuses might experience the same illusion as humans, indicating that they have a sense of body ownership similar to ours. All the octopuses tested responded to stimulation on the fake arm by changing their body color or attempting to escape. However, when researchers used other methods like asynchronous stimulation, the octopus showed no response.

These findings are intriguing as they open new avenues for understanding how octopuses perceive their bodies and interact with the world around them. According to Izuru Ikeda, one of the researchers involved in the study, such perception is considered an advanced human capability.

Conclusion

This study confirms that octopuses possess an advanced ability to perceive their bodies and interact with their surroundings based on this perception. Discovering that octopuses can fall for the same illusion experienced by humans paves the way for further research into how these intelligent marine creatures understand their internal and external worlds. These results could significantly impact how we study the cognition and behavior of marine animals in the future, prompting us to reconsider the neurological complexities of these fascinating sea creatures.