Cyborg prosthetics for limbs that don’t exist

18.15, Tuesday 7 Apr 2020

If you’re given a third arm coming out of the middle of your chest, a really long third arm, it turns out you can adapt to using it successfully in less than 10 minutes.

Homuncular Flexibility in Virtual Reality, Won et al (2015) [PDF].

What if you could become a bat–your arms acting as wings allowing you to fly through the night sky? The avatars that users inhabit in virtual reality (VR) make this possible. … For example, could people learn to control a lobster avatar that had many more limbs than its human user? … Tracked movements that the user made in the physical world would be rendered as different movements of the avatar body. Thus, an eight-armed lobster could have each limb powered by the rotation of a wrist, the flex of an ankle, or some combination of the two.


In Experiment Two, participants controlling three-armed avatars learned to hit more targets than participants in two-armed avatars.

And in the “Future directions” section:

how far can we push these adaptations? Can people learn to control eight limbs, or kilometer-long arms?

Okay so that’s VR, but why not really?

The Cave was a proto-VR environment where you would stand in a cube-shaped room where a virtual environment was projected on the walls. Using a controller, you could “move” through the virtual environment – and look around you without needing to use a headset.

I don’t have a reference for this but I heard about this experiment: what they did was track the rotation of your head, as you looked from side to side, and then rotate the virtual environment the same amount again. So if you looked 90 degrees the right, it would be as though you were looking 180 degrees, directly behind you.

What I heard was that people adapt surprisingly quickly to this. You get accustomed, really fast, to being able to rotate your head all the way round like an owl.

Dani Clode’s design provocation The Third Thumb visualises a robotic extra thumb as a sixth digit on the hand, used to hold fruit and play the guitar.

MobiLimb is a robotic finger that protrudes from a smartphone. It can prop itself up so you can see the screen; it can literally point things out; it can drag itself across the table.

Why don’t we see a ton of serious research into areas like this? Given it turns out we can adapt psychologically quite happily to having extra limbs, why don’t we see R&D money being piled in?

I want to see weird-ass research lab nerds from universities walking around like Doctor Octopus, doing their best to convince the rest of us that more hands = better. I want to see folks like Apple and Google try really, really hard to get it to go mainstream, even though they will mostly fail.

Because decades of research got us the iPhone – and, by extension, the peace dividend of the smartphone wars being: drones (sensors and batteries) and the internet of things (commodity connectivity) which is massive in the industrial world). Imagine if robotic prosthetics were cheap and commonplace.

What are the mundane, everyday applications?

I want an exoskeleton chairless chair but for gardening.

I want to open the door of a cafe with my third arm when my hands are full carrying coffee.

I want to feel electric fields with my fingertips. I want to go ambling in a new city and not get lost because I have an intuitive sense of north. I want a camera stuck on the back of my neck that shows up as a stretched image round the rim of my otherwise ordinary glasses, and I want to know how quickly seeing behind me feels like a little extra sense that I couldn’t do without.

Forget showing my lost items on a map on a screen and making me treasure-hunt my way back to them. I want to be able to whistle to my phone from anywhere in the house, and have it wriggle out of the sofa and scamper across the room and snuggle into my pocket.

Imagine giving your phone a high five with a tiny hand that you don’t yet have.

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