The relative immunity of the concept of size constancy in the face of chang
es to the retinal image as well as the pictorial device of linear perspecti
ve were investigated with 9 savant artists and 9 controls. For drawing use
of pictorial rules seemed independent of levels of intelligence; however, w
hen a construction instead of a drawing task had to be carried out, diagnos
is rather than the presence or absence of talent was the decisive factor.