Some people declare that they possess a personal visual representation
of numbers: some automatically ''see'' the numbers they are confronte
d with in a precise location in a structured mental space, others ''as
sociate'' specific colours with given numbers. Such visuo-spatial repr
esentations of numbers were first described by Galton in 1880 but have
since received little attention from psychologists. It is the aim of
this article to describe these mental representations and discuss thei
r role in number processing. The authors first review Galton's observa
tions, and then present their own. Finally, they discuss the relevance
of these visuo-spatial representations in relation to contemporary de
bates on number representation and calculation.