Human hands have had 10 digits for millions of years.
But it seems scientists at the University of Cambridge don’t think this is quite sufficient.
The experts have created the ‘Third Thumb’ – a controllable prosthetic that attaches to edge of the right hand.
It lets wearers pick up objects, open drinks bottles, sift through playing cards and even peel a banana – all with just one hand.
In their study, human volunteers quickly got used to the extra digit – which could ‘advance our motor capabilities beyond current biological limitations’.
Cambridge researchers have shown that people have little trouble in learning very quickly how to use a third thumb – a controllable, prosthetic extra thumb
The study was led by Tamar Makin, a professor of cognitive neuroscience at the University of Cambridge, and published in Science Robotics.
Professor Makin and colleagues think the thumb could be particularly valuable to amputees who have, for example, lost an arm, and have difficulty performing everyday tasks with just one hand.
‘Technology is changing our very definition of what it means to be human,’ they say in their paper.
‘Machines are increasingly becoming a part of our everyday lives and even our minds and bodies.
‘An exciting area for future technology is motor augmentation, which is designed to enhance or extend the physical capabilities of humans.’
The Third Thumb is worn on the opposite side of the palm to a person’s real thumb and controlled by a pressure sensor placed under each big toe or foot, which can fit inside a shoe.
Pressure from the right toe pulls the prosthetic digit across the hand, while the pressure exerted with the left toe pulls it towards the fingers and releasing pressure moves it back to its original position.
It lets wearers pick up objects, open drinks bottles, sift through playing cards and even peel a banana – all with just one hand
The additional digit could ‘advance our motor capabilities beyond current biological limitations’ the experts believe
In their study, the team tested 596 participants, ranging in age from three to 96 years old, who were given up to a minute to familiarise themselves with the device.
The thumb was provided in different sizes so they could fit the hands of children and adults.
The participants performed two tasks – firstly, picking up pegs and putting them in a basket, and secondly, manipulating and moving five or six different foam objects of various sizes.
Overall, the thumb was successfully worn and controlled by 99.3 per cent of the sample, the researchers found.
And 98 per cent of participants were able to successfully manipulate objects using the Third Thumb during the first minute of use.
Older and younger adults had a similar level of ability when using the device, although further investigation just within the older adults age bracket revealed a decline in performance with increasing age.
Third Thumb was provided in different sizes so they could fit the hands of children and adults
‘This effect could be due to the general degradation in sensorimotor and cognitive abilities that is associated with aging,’ the team say.
‘In addition, these effects could also reflect a generational relationship to technology.’
It’s unclear when or how the academics could make their device available to the public, or how much it would cost.
But they hope it ‘may pave the way for establishing a benchmark’ for other ‘inclusive’ human-centred devices.
‘Future augmentation technologies could have an extensive influence on society and be beneficial to many people,’ they write.