Professor Makin (UCL Institute of Cognitive Neuroscience), lead author of the study, said: “Body augmentation is a growing field aimed at extending our physical abilities, yet we lack a clear understanding of how our brains can adapt to it. By studying people using Dani’s cleverly-designed Third Thumb, we sought to answer key questions around whether the human brain can support an extra body part, and how the technology might impact our brain.”

The Third Thumb is 3D-printed, making it easy to customise, and is worn on the side of the hand opposite the user’s actual thumb, near the little (pinky) finger. The wearer controls it with pressure sensors attached to their feet, on the underside of the big toes. Wirelessly connected to the Thumb, both toe sensors control different movements of the Thumb by immediately responding to subtle changes of pressure from the wearer.

For the study, 20 participants were trained to use the Thumb over five days, during which they were also encouraged to take the Thumb home each day after training to use it in daily life scenarios, totalling two to six hours of wear time per day.

“Our study shows that people can quickly learn to control an augmentation device and use it for their benefit, without overthinking. We saw that while using the Third Thumb, people changed their natural hand movements, and they also reported that the robotic thumb felt like part of their own body.”

First author of the study, Paulina Kieliba (UCL Institute of Cognitive Neuroscience) said: “Body augmentation could one day be valuable to society in numerous ways... we need to continue researching the complicated, interdisciplinary questions of how these devices interact with our brains.”

(Read more at UCL News)

Science fiction writers have imagined this possible future. Fans of Star Trek: The Next Generation may recall the episodes "Coming of Age" and "A Matter of Honor" and the Benzites with two thumbs.

(Star Trek: TNG Benzites with two thumbs)

I'd also mention the human augmentation described in terrific, creative detail in Samuel R. Delany's Nebula award-winning 1968 novel Babel-17. In particular, consider these decorative implants:

The Officer pushed open the door of PIastiplasm Plus ("Addendums, Superscripts, and Footnotes to the Beautiful Body").

"It's listed in your catalog as 5463," the Customs Officer declared. "I want it there." He clapped his left hand to his right shoulder. P<> The surgeon returned ... with a tray full of fragments. The only recognizable one was the front half of a miniature dragon with jeweled eyes, glittering sc ales, and opalescent wings: it was less than two inches long.

"When he's connected up to your nervous system, you'll be able to make him whistle, hiss, roar, flap his wings and spit sparks..."
(Read more about Samuel R. Delany's decorative implants)