Researchers at the University of Cambridge have demonstrated that the public can quickly learn to use a controllable prosthetic extra thumb—dubbed the "Third Thumb"—to pick up and manipulate objects. This finding comes from a study involving a diverse range of participants, highlighting the potential for inclusive technological advancements.
Motor Augmentation and Inclusivity

Motor augmentation, which involves using motorized wearable devices like exoskeletons or robotic body parts to enhance our physical capabilities, is an emerging technology. These devices can boost productivity for healthy individuals and provide new ways for people with disabilities to interact with their environment.

Professor Tamar Makin from the Medical Research Council (MRC) Cognition and Brain Sciences Unit at Cambridge emphasized the importance of inclusivity in technology development. "Technology is changing our very definition of what it means to be human," she said, noting that machines are increasingly integrating into our daily lives and bodies. Makin stressed the need to ensure these technologies benefit all people, including marginalized communities often excluded from innovation.
The Third Thumb: Design and Testing

Dani Clode, a collaborator in Professor Makin's lab, developed the Third Thumb to increase the wearer's range of movement and enhance their grasping capability. The device, worn on the opposite side of the palm from the biological thumb, is controlled by pressure sensors under each big toe. Pressure from the right toe moves the Thumb across the hand, while pressure from the left toe moves it toward the fingers. The Thumb’s movement is proportional to the pressure applied, and it returns to its original position when pressure is released.

In 2022, the team tested the Third Thumb at the Royal Society Summer Science Exhibition, where participants of all ages used the device for various tasks. Published in Science Robotics, the study involved 596 participants aged three to 96 from diverse backgrounds. Only four participants were unable to use the Thumb due to fit issues or difficulty with foot control.
Tasks and Results

Participants had up to a minute to familiarize themselves with the Third Thumb before performing one of two tasks:

    Pegboard Task: Using only the Third Thumb, participants picked up pegs from a pegboard and placed them in a basket, aiming to move as many pegs as possible in 60 seconds. This task was completed by 333 participants.

    Foam Objects Task: Participants used both the Third Thumb and their biological hand to manipulate and move various foam objects of different shapes, which required different manipulations. They aimed to move as many objects as possible into a basket within 60 seconds. This task was completed by 246 participants.

Remarkably, 98% of participants successfully manipulated objects with the Third Thumb within the first minute, with only 13 participants unable to perform the task. Ability levels varied, but there were no significant differences in performance between genders, nor did handedness affect performance despite the Thumb always being worn on the right hand. Additionally, there was no clear advantage for individuals considered 'good with their hands,' such as musicians or those in manual dexterity jobs.

This study underscores the potential for motor augmentation devices to be quickly adopted and used effectively by a broad range of people, paving the way for more inclusive technological advancements.