The representation of extendedness in children's drawings of sticks and discs. 
Piaget has suggested that the reason why children find it difficult to draw foreshortened views is because they lack any conscious awareness of their own viewpoint.  Instead, it is proposed that most of these difficulties derive from the constraints of drawing as a representational system: for example, although a round region shows a true view of a foreshortened stick, it is unsatisfactory as a representation.  To test between these alternative proposals, 4-, 7-, and 12-year-olds were asked to draw sticks and discs in foreshortened and nonforeshortened positions.  As predicted, fewer 7- and 12-year-olds used a round region to represent a foreshortened stick, compared with children of the same age who used a long region to represent a foreshortened disc.  In addition, the 12-year-olds used a different and more effective denotation system compared with the 7-year-olds.