A group of 36 healthy participants were trained on the device (professional musicians were excluded) and used it to perform a variety of tasks, such as building a tower of blocks, manipulating multiple balls simultaneously, or stirring a coffee cup with a spoon. They even managed to perform some of these tasks while blindfolded or distracted with math problems. “The Third Thumb is a flexible 3D-printed thumb extension for your hand, controlled by your feet,” said Clode, a designer at UCL. “It is worn on the hand, next to your little finger, and dynamically moves like a thumb by using...