The Human Octopus: controlling supernumerary hands with the help of virtual reality

We investigated the "human octopus" phenomenon where subjects controlled virtual supernumerary hands through hand tracking technology and virtual reality. Four experiments were developed to study how subjects (n=10) operate with different number and behaviour of supernumerary hands. The behaviours involved inserting movement delays to the virtual hands and adjusting their movement scale or position. It was found that having more hands to operate with does not necessarily mean higher success rate while performing a certain task. However, supernumerary hands could be made more effective by adjusting the associated movement scales of the extra hands. The subjective feeling and ownership of the hands diminished when a delay was inserted for the virtual hands or when their position was altered.