Numerical cognition: what can we learn from blind people?

The representation of numbers is assumed to interact with two visuo-motor functions. On the one hand, following the observation that children often use their fingers to learn the counting sequence and basic arithmetic operations, numbers were assumed to interact with finger movements. On the other hand, following the recurrent observation that small numbers are preferentially associated with the left side of space while large numbers are preferentially associated with the right side of space, numbers were assumed to interact with space. In this paper, we will examine the role vision plays in shaping these interactions between fingers and numbers and between numbers and space. To this aim, different experiments with blind and sighted people will be detailed. The role of developmental vision on the development of the finger-numeral representation will first be examined. Then we will investigate the influence of developmental vision on the visuo-spatial representation of numbers.