Field studies by University of Chicago psychologist Susan Goldin-Meadow and a team of researchers found deaf people in Nicaragua, who had not learned formal sign language, do not have a complete understanding of numbers greater than three.
When it comes to counting, a remote Amazonian tribespeople have been found to be lost for words.
Researchers discovered the Piraha tribe of Brazil, with a population of 200, have no words beyond one, two and many.
The word for "one" can also mean "a few", while "two" can also be used to refer to "not many".
Peter Gordon of Columbia University in New York said their skill levels were similar to those of pre-linguistic infants, monkeys, birds and rodents.