Images of numbers, or when 98 is upper left and 6 sky blue

Some people declare that they possess a personal visual representation of numbers: some automatically ''see'' the numbers they are confronted with in a precise location in a structured mental space, others ''associate'' specific colours with given numbers. Such visuo-spatial representations 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 their role in number processing. The authors first review Galton's observations, and then present their own. Finally, they discuss the relevance of these visuo-spatial representations in relation to contemporary debates on number representation and calculation