Learning to use a handy Third Thumb may be easier than you think

Having an extra thumb on one hand may massively boost your manual dexterity, but wouldn't it be hard to learn to use? Not according to a new study, which found that the majority of a wide variety of people got the hang of the thing in just one minute.

We first heard about the Third Thumb back in 2017, when it was created by British designer Danielle Clode as her Masters graduate project at the Royal College of Art in London.

At the heart of the device is the 3D-printed articulated Thumb itself, which is strapped onto the user's right hand so it sits opposite their natural thumb. A cable connects the Thumb to a wrist-worn motor module, which is in turn wirelessly linked to two pressure sensors – one under each of the user's big toes.

Exerting toe pressure on the right-side sensor pulls the Thumb laterally across the hand, whereas pressure on the left sensor pulls the digit up toward the fingers. The greater the toe pressure, the faster the Thumb moves. Releasing toe pressure causes the Thumb to go back to its "home" position.

When neuroscientists from University College London saw the Third Thumb on the news, they contacted Clode about using the device in their research on body augmentation. In an ensuing 2021 study, 20 volunteers were given five days to learn to use the appendage, and were encouraged to practice for two to six hours every day. While the research did show how use of the Thumb caused significant changes to activity in the brain’s sensorimotor cortex, it didn't provide much of an indication of how well the technology could be utilized by a wide range of people.

That's where the new University of Cambridge study comes in.

It's based on data gathered in 2022, when members of the public were invited to use the Thumb at the annual Royal Society Summer Science Exhibition. Over a five-day period, a total of 596 participants were given just one minute to familiarize themselves with the device. The test subjects reportedly represented "a wide range of demographic backgrounds," and ranged in age from three to 96 years old.

All but four of the individuals were able to purposefully move the Thumb after the 60-second training session, the exceptions being small children who couldn't exert enough toe pressure, and people whom the setup didn't securely fit. What's more, all but 13 of the participants were able to manipulate objects with the Thumb.

Taking things a step further, the volunteers were asked to perform two specific tasks after the one-minute orientation. The first of these involved using just the Thumb to pick pegs out a pegboard and place them in a basket, moving as many pegs as possible within 60 seconds. A total of 333 participants were able to do so.

The second task involved using the Thumb along with the hand to pick and place a number of foam objects of different shapes and sizes, once again moving as many as possible within one minute. In this case, 246 people completed the exercise.

Importantly, it was found that there was no difference in performance between genders, or even between left- and right-handed people (despite the fact that the Third Thumb is right-hand-only).

There was also little difference in the performance of younger and older adults, although within the "older" group, performance did tend to decrease with age. This may have been due to deterioration of sensorimotor and cognitive skills, or it may simply have been a matter of older people generally being less technologically inclined.

It is hoped that once the Third Thumb is developed further, it could be used not only to boost the abilities of able-bodied users, but also to aid people with diminished manual dexterity.

"Augmentation is about designing a new relationship with technology – creating something that extends beyond being merely a tool to becoming an extension of the body itself," says Clode, who is now a collaborator within the lab of the lead scientist, U Cambridge's Prof. Tamar Makin. "Given the diversity of bodies, it's crucial that the design stage of wearable technology is as inclusive as possible. It's equally important that these devices are accessible and functional for a wide range of users."

A paper on the study was recently published in the journal Science Robotics. You can see the Third Thumb in action, in the video below.

Source: University of Cambridge