A Third Thumb??!! ... Researchers at the University of Cambridge in England have been messing around with a gadget that gives people a "third thumb" to expand their range of motion. And even though humans have had only 5 digits on their hands for millions of years, the researchers found that it was easy for people to get used to having that extra thumb to grip and manipulate objects. A staggering 98 percent of people were able to use this "third thumb" -- with only 13 percent unable to figure it out within the first minute.