Representing the position of the objects independently from our own position is a fundamental cognitive ability, which also influences numbers representation. In fact, in cultures where writing proceeds from-left-to-right, numbers are spatially represented according to an equivalently oriented small-to-large ‘number line’. In a series of studies we investigated whether spatial and numeric representation depends on visual experience. We tested congenitally blind, late blind and blindfolded sighted participants who haptically learnt table-top or room-sized regularly shaped arrays of objects to determine which spatial reference frame was used. Additionally, to determine the role of developmental vision on number representation the same three groups were tested in a random number generation task where they had to alternately turn their head left or right before generating a number. In the spatial tasks, we found that blindfolded sighted and late blind participants that is, those with visual experience, showed a preferential use of the object-based or ‘allocentric’ reference frame. On the contrary, congenitally blind participants preferred a self-based, or ‘egocentric’, reference frame. In the numeric task, consistently with the standard number-line participants with visual experience preferred to generate smaller numbers when looking left and larger numbers when looking right. In contrast, participants without any visual experience showed the opposite pattern of results. These results suggest a role for visual experience in the development of spatial and numerical representations by fostering allocentric spatial representation, and provide converging evidence for visually-driven development of the parietal cortex.
P.S: The seminar will be in English.