THE MAGNITUDE OF THE POGGENDORFF ILLUSION AS A FUNCTION OF AGE

Abstract

The magnitude of the Poggendorfg illusion decreases with age from 5 to approximately 10 years, after which it remains stable into old age. The magnitude of the illusion is approximately 60 of arc among the youngest observers, decreasing to an asymptotic level of approximately 30 of arc. The illusion is greater among feeble-minded observers independent of chronological age. Analysis of the basis for the illusion does not unequivocally support any 1 theoretical approach.