Projected afterimages after manipulation of cognitive schemes in children.

Telling one group of subjects that afterimages are a physical reality largely independent of the observer and another group that afterimages are projected by the subject himself, it was predicted that the afterimages in these groups would differ. In all 10 pairs of nine-year-old children, matched with respect to cognitive maturity, the subject getting the former instruction reported more size-constant and/or positive afterimages than the subject getting the latter instruction.