A developmental study of the effects of instructions on visual shape judgements.

Previous developmental studies of visual shape judgements have failed to instruct subjects clearly as to the type of shape judgements required. Using the method of adjustment 180 subjects in five age groups, 6, 8, 10, 12 and 19 years, were instructed to judge either the real or projected shape of an elliptical standard slanted 39, 57 and 72 degrees from the fronto-parallel. No age changes were found in the tendency towards shape constancy. Objective shape judgements exhibited a significantly greater degree of constancy than projective judgements and there was no decline in constancy with increasing slant of the standard under objective instructions, in contrast to a marked decline under projective instructions. Female subjects consistently manifested a greater tendency towards shape constancy than males.