While a large literature has investigated perception of space in both normal people and patients with brain damage, little is known as to the cognitive processes involved in tasks explicitly requiring the mental measurement of visual space (relative distance estimation, size comparison, etc.). The project follows up on research investigating the Landmark Task (e.g. Toraldo et al., 2010), The Distance Judgement Task (Toraldo, 2003) and others, both in normal subjects and in brain-damaged patients with neglect and/or hemianopia.