Children understand numbers differently than adults. For kids, one and two seem much further apart then 101 and 102, because two is twice as big as one, and 102 is just a little bigger than 101.
It's only after years of schooling that we're persuaded to see the numbers in both sets as only one integer apart on a number line.
Dror Dotan, a doctoral student at Tel Aviv University's School of Education and Sagol School of Neuroscience said that he was surprised after seeing that people never completely stop thinking about numbers like they did when they were kids.
He said that the innate human number sense has an impact, even on thinking about double-digit numbers.
The findings, a significant step forward in understanding how people process numbers, could contribute to the development of methods to more effectively educate or treat children with learning disabilities and people with brain injuries.
On the iPad used in the study, the participants were shown a number line marked only with "0" on one end and "40" on the other.
Numbers popped up one at a time at the top of the iPad screen, and the participants dragged a finger from the middle of the screen down to the place on the number line where they thought each number belonged. Software tracked the path the finger took.
Statistical analysis of the results showed that the participants placed the numbers on the number line in a linear way, as expected. But surprisingly - for only a few hundred milliseconds - they appeared to be influenced by their innate number sense.