Direct and pairwise area estimation of physical shapes through vision and touch

On a perceptual task in which a participant estimated areas of five physical rigid shapes, participants could view and touch the shapes, using one of two estimation methods, direct or pairwise. For the direct method, participants held one shape at a time and estimated the area based on a unit square (equal to 1/10 of the actual area). Mean error by participants was 14.4%. In the pairwise method, when participants were simultaneously handed two shapes, their error was 0.3%. Both direct and pairwise errors for vision plus touch of physical stimuli were considerably lower than previous errors made when viewing with an overhead projector screen.