For those who fondly remember their slide rules (and especially those that still prefer the slip stick to the pocket calculator) I think this excerpt from Here’s Looking at Euclid is quite interesting.
“In one of his most fascinating experiments, [scientists and linguist Pierre] Pica examined the [South American Munduruku] Indians’ spatial understanding of numbers. How did they visualize numbers spread out on a line? In the modern world, we do this all the time-on tape measures, rulers, graphs and house numbers along a street. Since the Munduruku don’t have numbers, Pica tested them using sets of dots on a screen. Each volunteer was shown an unmarked line on the screen. To the left side of the line was one dot, to the right ten dots. Each volunteer was then shown random sets of between one and ten dots. For each set the subject had to point at where on the line he or she thought the number of dots should be located. Pica moved the cursor to this point and clicked. Through repeated clicks, he could see exactly how the Munduruku spaced numbers between one and ten.
“When American adults were given this test, they placed the numbers at equal intervals along the line. They re-created the number line we learn at school, in which adjacent digits are the same distance apart as if measured by a ruler. The Munduruku, however, responded quite differently. They thought that intervals between the numbers started large and became progressively smaller as the numbers increased. For example, the distances between the marks for one dot and two dots, and two dots and three dots, were much larger than the distance between seven and eight dots, or eight and nine dots.
“The results were striking. It is generally considered a self-evident truth that numbers are evenly spaced. We are taught this at school and we accept it easily. It is the basis of all measurement and science. Yet the Munduruku do not see the world like this. They visualize magnitudes in a completely different way.