Got a Minute? Why Not Learn To Operate a ‘Third Thumb’

A team of researchers from the Medical Research Council (MRC) Cognition and Brain Sciences Unit at the University of Cambridge have put a new robotic thumb to the test to see how easy it is for users to pick up.¹ They demonstrated that members of the public, including children as young as three and adults as old as 96, can learn quickly and deftly to operate the robotic body part. Ninety-eight percent of participants could successfully manipulate objects with the extra thumb in the first minute, regardless of gender, handedness, or hand-related hobbies.

This study, which included 596 participants, was conducted over five days during the annual Royal Society Summer Science Exhibition 2022. The results published in Science Robotics 2024 highlight how effortlessly we can adopt and integrate robotic devices into our daily lives.

What is an extra robotic body part? A third thumb, you say?

Extra robotic body parts extend the range of a human’s movement beyond what their natural limbs can do.² These technologies include prosthetics designed for people with impairments, such as amputees or stroke patients. Just imagine how life-changing it could be for someone who has lost fingers or suffers from neuronal atrophy to regain functionality in their hand. Think about what you would do if you had an extra body part like the third thumb. For healthy people robotic innovations enhance physical strength and speed, extend natural limbs’ reach, and improve control over tools and machinery. Others may add new movement abilities, potentially transforming how humans interact with their surroundings.  

So, why aren’t we already seeing these extra appendages in sale in electronic stores? The hold-up has been the human-robotic interface. But guess what? Recent advances are starting to change that. The extra robotic body parts typically need a control interface for users to command and feedback devices that provide information about the device².

The Third Thumb is a 3-D printed extra robotic body part that augments the wearers’ movement ability enhancing dexterity. It attaches to the palm opposite the natural thumb and can move in two ways. Motors on the wrist power it, and the user controls its movements using pressure sensors under each big toe. By pressing down with one toe, you can move the thumb sideways across your hand. Pressing with the other toe makes the thumb move upwards towards your fingers. Sounds pretty simple, right? But just how challenging is using feet to control your hands? Is it as easy as it sounds? Brain and cognition researchers led by Professor Tamar Makin put the Third Thumb to the test in a series of experiments.  

Testing The Tech

Cambridge University researcher and the inventor of the third thumb Dani Clode collaborated with the Neuroscience unit including Lucy Dowdall and Tamar Makin to adapt the Third Thumb for public testing. This included developing pressure sensors for exhibition use, ensuring the Third Thumb is suitable for a wide range of participants.

People of all genders and handedness successfully used the device, setting the bar high for other inventors to design inclusive experiments. In the past, technological developments, such as speech recognition systems biased against certain voices or safety designs that did not consider female physiology, highlighliting the risks of not prioritizing inclusivity. Starting with testing different people and adapting to their requirements can help avoid those same mistakes. Lucy Dowdall, a co-author of this study, said, ‘We’ll need to factor in different ages, genders, weight, lifestyles, disabilities – as well as people’s cultural, financial backgrounds, and even likes or dislikes of technology. Physical testing of large and diverse groups of individuals is essential to achieve this goal.’³  This vision provides an insight into the sound research design by the Cambridge researchers that goes beyond the rapid commercialization of new technology. 

Thumbs Up

For the first task (pegboard challenge), the participants used the Third Thumb to pick up pegs from a pegboard and place them in a basket, with 333 participants completing it. For the second challenge, participants used the third thumb with their biological hand to manipulate and move foam objects into a basket, and 246 participants completed this task. Similar ability levels are found among older and younger adults, though performance declined with increasing age among older adults. Younger children (under 10) generally performed worse than older children and adults. Since 98% of participants successfully wore, operated, and performed tasks with the Third Thumb during the first minute, the researchers concluded that this device is ‘user-friendly’¹. 

Is this for real? Are we all turning into ‘Bionic Humans’?

This is just the beginning of redefining human capabilities, and devices can transform various professions, from musicians to surgeons, by enabling workers to perform previously difficult or impossible tasks. The extra thumb can handle everyday tasks like holding a deck of playing cards, carrying extra shopping bags, holding your phone to get a selfie, or keeping food steady while you cut it, boosting your natural abilities safely. The study brings hope to the impaired, positively impacting their quality of life and creating avenues for future robotic extensions and prosthetics. 

Although the designer and neuroscientist duo Clode and Makin demonstrated the potential of the Third Thumb, several factors need attention before its universal application. Researchers have previously studied how human-tool interaction affects the brain, noting changes in neural adaptation, body representation, and self-perception⁴.

Evolving Ideas

The Cambridge research group builds on this understanding by examining the changes in neural connections, emphasizing the need to consider the neurocognitive effects of human-robot integration on body representation and motor control.⁵ Moreover, continuous technological evolution and advances in sensors and control mechanisms will make these devices more intuitive, affordable, and acceptable.

Regulations, privacy and safety drive acceptance and trust, while ethical concerns must match human sensitivities. The involvement and support from major funding bodies like the European Research Council, Wellcome, the Medical Research Council, and the Engineering and Physical Sciences Research Council underline the significance and credibility of this research, paving the way for further development and implementation of inclusive motor augmentation technologies.

What’s next for the Third Thumb? 

Motor augmentation technologies like the Third Thumb are on the cusp of wider adoption, driven by ongoing research and promising study results. The key to their future is identifying practical applications and demonstrating their benefits. Addressing concerns about human identity, agency, and ethical use is crucial for building acceptance. With continued development, regulatory support, and public engagement, these technologies could soon become integral to various aspects of daily life, enhancing human capabilities and improving the quality of life for many.

References

1. Clode D., Dowdall L., da Silva E., et al. Evaluating initial usability of a hand augmentation device across a large and diverse sample. Sci Robot. 2024;9(90):eadk5183. doi:10.1126/scirobotics.adk5183 ↩︎
2. Eden J, Bräcklein M, Ibáñez J, et al. Principles of human movement augmentation and the challenges in making it a reality. Nat Commun. 2022;13(1):1345. Published 2022 Mar 15. doi:10.1038/s41467-022-28725-7 ↩︎
3. Lucy Dowall’s Quote https://www.cam.ac.uk/stories/third-thumb ↩︎
4. Di Pino G, Maravita A, Zollo L, Guglielmelli E, Di Lazzaro V. Augmentation-related brain plasticity. Front Syst Neurosci. 2014;8:109. Published 2014 Jun 11. doi:10.3389/fnsys.2014.00109  ↩︎
5. Kieliba P, Clode D, Maimon-Mor RO, Makin TR. Robotic hand augmentation drives changes in neural body representation. Sci Robot. 2021;6(54):eabd7935. doi:10.1126/scirobotics.abd7935 ↩︎