We’ve previously seen drummers with three arms, and robotic sixth fingers for stroke patients. Now, a project called The Third Thumb has shown how the brain adapts to an extra body part. The Third Thumb is the work of Dani Clode, a designer and researcher at University College London’s Plasticity Lab. Her device is a 3D-printed prosthetic that is controlled by the feet.
Pressure sensors underneath the big toes detect movement and relay that information via Bluetooth to a watch strap, which is equipped with two motors that control the thumb via Bowden cables similar to those used in bike brakes. The lexible thumb has two degrees of freedom (each controlled by a big toe), and it moves uncannily like the real thing.
In a recent study published on the preprint server bioRxiv (an online archive of studies that are yet to be peer-reviewed or published in a journal), Clode and her colleagues investigated what happens in the brain when people gain an extra digit. Over five days, they trained volunteers to use the thumb, asking them