Robotic augmentation can transform human bodies — but at a psychological cost

How great it would be to have an extra pair of hands? Carrying your groceries and opening doors would no longer be a balancing act. Brushing your teeth, hair, and readying the razor all at once would significantly cut your grooming time. Frying up steak and reaching for the salt while also opening the oven would be easy — dinner in minutes.

It all sounds good, but would having extra hands actually be good? Thanks to scientists from University College London, you can wonder no more.

“Humans have always been fascinated by augmentation; tools enhance our hands’ functionality — but what happens when we extend our actual hands?” the study’s first author and research assistant at the university’s Plasticity Lab, Paulina Kieliba, says in an interview.

What’s new — In a study published Wednesday in the journal Science Robotics, the team describe how they outfitted 36 participants with an extra robotic thumb, called the Third Thumb, to see how they could adapt to its use. The augmentation was designed by coauthor and senior research technician, Dani Clode, and is just a taste of what humans can expect in the future.

Just because we can augment our bodies with technology doesn’t necessarily mean we should — at least not without figuring out how it affects our brains first. In this study, the team found that even small augmentations can have a big impact on how our brains recognize our own bodies, including shrinking that recognition altogether.

“In recent years, the interest in augmentation technology has been growing rapidly,” Kieliba says in the same interview. “But we are still lacking answers to some very fundamental questions, such as: Can the human brain support an extra body part?”

Why it matters — Wielding a non-prosthetic, robotic thumb today might be a bit of a party trick, but in the future, these kinds of augmentation could become essential for labor-intensive jobs. Understanding how this technology might affect workers today before such devices are widely used will be essential to ensuring a safe implementation in the future, the team writes.

“[I]t is crucial for future research to look at dynamic effects of augmentative technology,” said Kieliba. “[In the future,] would people wearing extra arms for a prolonged period of time, for example, while working in the factory, be able to efficiently re-adapt to their natural body movements when driving home afterwards? We must ensure that these devices are safe to use, even after the user takes them off.”

What they did — Once the research team had strapped the Thumbs onto participants (a control group had a non-functional, additional thumb), they then had five days to adapt and learn how to use their new Thumbs, both in the lab and at home.

The Thumb itself differs from other experimental augmentation devices because it is wireless — it is powered by the users’ toes instead of a brain-computer interface — and so can be used both inside the lab and at home. Kieliba says this allows researchers to better “see how taking advantage of the extra thumb changes the way people use their hands.”

To guide the adaptation process, the researchers asked participants to complete three different types of tasks, including:

• Shared supervision: The Thumb is used to extend the grip of the biological hand — like if you were trying to carry one extra wineglass at a time.
• Collaboration tasks: The Thumb is used with another biological finger to pick up objects — for example, pinching a piece of food up from a board.
• Individualization tasks: Participants focus on motor control of their Thumb, while the biological hand was occupied — essentially, doing one thing with your actual hand and another with the Thumb.

Participants got the hang of their new Thumbs really quickly and showed significant improvements across the board on all their motor tasks. But these improvements seem to come with a worrying neural trade-off, Kieliba says.

“[U]sing an extra robotic thumb — it is not neutral to the brain,” Kieliba says in the report. “For people to use the augmentative technology efficiently, they need to change the way they use their natural fingers; they need to create new movement synergies; and by doing that, [they] update the way their body is represented in the brain.”

When the team placed participants in an fMRI (sans Thumb) to see how their brains might have changed as a result of the experience, they noticed a distinctive “shrinkage” in how participants mentally represented and understood their own hand. In particular, the neural representation of individual fingers had condensed. This is not the case for people who lose a hand, according to the researchers.

“[E]ven after the most profound change to the hand-arm amputation, the representation of the amputated hand remains stable in the brain,” Kieliba says in the report. “So, to see it change, after only five days of using the Third Thumb is not trivial to us!”

What’s next — This study doesn’t tell us how larger augmentations to the human body using robotics might affect our brains, but for now, the research team is looking to improve the use and study of the Thumb. One of the innovations they want to make is to allow people to use it while walking, and while in an fMRI scanner.

In the future, it will be especially important to consider how these technologies might affect people whose brains aren’t quite set in stone — like children and adolescents, Clode says in the report.

“It is really important for the researchers to consider the effects of augmentative technologies on potentially vulnerable populations,” Clode says in the interview. A third, robotic thumb might seem like a novel toy — but the effects are not child’s play.

“For example, what would happen if we give these devices to children or adolescents — how would augmentation impact their vastly more plastic brains?”

“We need to ensure that by learning to control an augmentation device, we are not negatively impacting the motor capabilities of the biological hand and body,” Clode adds.

Abstract: Humans have long been fascinated by the opportunities afforded through augmentation. This vision not only depends on technological innovations but also critically relies on our brain’s ability to learn, adapt, and interface with augmentation devices. Here, we investigated whether successful motor augmentation with an extra robotic thumb can be achieved and what its implications are on the neural representation and function of the biological hand. Able-bodied participants were trained to use an extra robotic thumb (called the Third Thumb) over 5 days, including both lab-based and unstructured daily use. We challenged participants to complete normally bimanual tasks using only the augmented hand and examined their ability to develop hand-robot interactions. Participants were tested on a variety of behavioral and brain imaging tests, designed to interrogate the augmented hand’s representation before and after the training. Training improved Third Thumb motor control, dexterity, and hand-robot coordination, even when cognitive load was increased or when vision was occluded. It also resulted in increased sense of embodiment over the Third Thumb. Consequently, augmentation influenced key aspects of hand representation and motor control. Third Thumb usage weakened natural kinematic synergies of the biological hand. Furthermore, brain decoding revealed a mild collapse of the augmented hand’s motor representation after training, even while the Third Thumb was not worn. Together, our findings demonstrate that motor augmentation can be readily achieved, with potential for flexible use, reduced cognitive reliance, and increased sense of embodiment. Yet, augmentation may incur changes to the biological hand representation. Such neurocognitive consequences are crucial for successful implementation of future augmentation technologies.