• Posted May 30, 2024

Coming to Grips With a Third Thumb

A “Third Thumb” -- a robotic, prosthetic extra thumb -- is easy to use and can help folks grab and tote more objects, a new study says.

Hundreds of diverse test subjects at a science exhibition were able to figure out the extra thumb quickly and use it to pick up things like pegs and foam objects, researchers reported May 29 in the journal Science Robotics.

“Technology is changing our very definition of what it means to be human, with machines increasingly becoming a part of our everyday lives, and even our minds and bodies,” said researcher Tamar Makin, a professor with the University of Cambridge's Medical Research Council Cognition and Brain Sciences Unit.

An emerging area of technology is motor augmentation – using wearable devices like extra robotic body parts to upgrade human motor capabilities beyond their current limits, researchers said.

The Third Thumb is worn up just under the pinky finger and held in place by a wrist strap.

It's operated by pressure sensors under the big toe of each foot, researchers explained. The right toe pulls the thumb across the hand in a gripping motion, while the left toe pulls the thumb up firmly against the natural fingers.

The gadget is aimed at increasing the wearer's range of movement, enhancing their ability to grasp large objects, and expanding the carrying capacity of the hand, the researchers said.

They gave the Third Thumb a road test during the 2022 Royal Society Summer Science Expedition, at which 596 people ages 3 to 96 strapped on the thumb and performed some manual tasks.

About 98% of participants were able to manipulate objects using the Third Thumb after wearing it for about a minute, researchers said.

The test subjects were given a pair of one-minute tasks to see how helpful a Third Thumb might be:

• About 333 participants completed a task in which people used the Third Thumb alone to pick up pegs from a pegboard and put them in a basket.

• About 246 subjects used the Third Thumb with the rest of their hand to manipulate or move up to six different foam objects of various shapes.

• Both genders worked the Third Thumb about as well, but researchers noted that performance declined in older adults. Children and younger teens also struggled to use the thumb.

• There was no evidence that people who could be considered “good with their hands” -- because they play a musical instrument or have a job involving manual dexterity, for instance -- were better using the Third Thumb than others.

These results will help researchers better adapt the Third Thumb for use in more people.

“Given the diversity of bodies, it's crucial that the design stage of wearable technology is as inclusive as possible,” said researcher Dani Clode, who developed the Third Thumb at Cambridge.

It's equally important that these devices are accessible and functional for a wide range of users,” Clode added in a university news release. “Additionally, they should be easy for people to learn and use quickly.”

More information

Georgia Tech has more about motor augmentation.

SOURCE: University of Cambridge, news release, May 29, 2024