Number magnitude and grip aperture interaction.

Behavioural, neuropsychological and functional imaging studies suggest possible interactions between number processing and finger representation. Since grasping requires the object size to be estimated in order to determine the appropriate hand shaping, coding number magnitude and grasping may share common processes. In the present study, participants performed either a grip closure or opening depending on the parity of a visually presented digit. Electromyographic recordings revealed that grip closure was initiated faster in response to small digit presentation whereas grip opening was initiated faster in response to large digits. This result was interpreted in reference to a recent theory which proposed that physical and numerical quantities are represented by a generalized magnitude system dedicated to action.