Give a person a virtual reality arm four times its usual length, and they'll soon be feeling it as if it were their own, say University of Barcelona scientists.
(Personally, if we were going to extend a limb to that sort of length we'd have picked a different one - but an arm it was. They like to keep it clean, these scientists.)
In their experiment, fifty people were given a head-mounted display to place them in a virtual world, and with a virtual body.
Their dominant hand was placed on a table with a special textured material. They could feel this with their real hand, but also see their virtual hand touching it; and as they moved their real hand over the surface of this table they saw the virtual hand doing the same.
And, found the team, even when the virtual arm was four times the length of the real one, some 40 to 50 percent of people had the illlusion that it was their own.
The reason seems to be the importance of visual clues, as whe the real hand touched the table and the virtual one didn't, the effect still held.
"These results show how malleable is our body representation, even incorporating strong asymmetries in the body shape, which do not correspond at all to the average human shape," say the researchers.
"This type of research will help neuroscientists to understand how the brain represents the body, and ultimately may help people overcome illnesses that are based on body image distortions."