Some people think of numbers as having positions in space. These are number-space synaesthetes! Different people’s number-space synaesthesia layouts look quite different, so for some people they look like a line moving from left to right, for others right to left, for others a circle or a grid or a complex swirly thing
I was interested in whether the direction you count on your fingers (starting on the left or on the right) might be linked to how your number-space synaesthesia looks.
Jamie Ward kindly lent me his filing cabinet of questionnaires recording synaesthetes’ number-space layouts, and then I contacted those synaesthetes to ask about how they counted to 10 on their fingers.
Surprisingly, finger-counting direction and number-space synaesthesia layouts have no connection. I don’t know why this is, but one possibility is that having synaesthesia means you don’t need to use your fingers when you learn to count. Fingers are the basis of counting for a lot of people, so if synaesthetes didn’t use their fingers in the same way when they were learning, that could explain other research showing that synaesthetes are slower than other people at some types of mental arithmetic.
