The ups and downs (and lefts and rights) of synaesthetic number forms: Validation from spatial cueing and SNARC-type tasks

Abstract

Typically, numbers are spatially represented using a mental 'number line' running from left to right. Individuals with number-form synaesthesia experience numbers as occupying specific spatial coordinates that are much more complex than a typical number line. Two synaesthetes (L and B) describe experiencing the numbers 1 through 10 running vertically from bottom to top, 10-20 horizontally from left to right, 21-40 from right to left, etc. We investigated whether their number forms could bias their spatial attention using a cueing paradigm and a SNARC-type task. In both experiments, the synaesthetes' responses confirmed their synaesthetic number forms. When making odd-even judgments for the n..