Optico-geometrical illusions may be dichotomized into those whose magnitudes decrease with an increase in chronological age (Type I) and those whose magnitudes increase with chronological age (Type II). The former illusions appear to be determined largely by stimulus variables and the state of the receptor system, and not at all by intellectual functions. The latter appear to depend upon the comparison of visual stimuli separated by space or time, such comparisons seeming to necessitate intellectual functioning. In this experiment the method of presentation of a Type I illusion was altered so that its parts were presented in succession rather than simultaneously. It was predicted that such alteration would reverse the direction of illusion, reverse its developmental pattern, and would produce a correlation with measured intellectual capacity, all of which would be characteristic of a Type II illusion. Ss were school children in Grades 2 to 5. All predictions were confirmed. The implications of the results for an overview of perception in general were discussed.
Mueller-Lyer figures produced by lightness contrast (white on black) and by hue contrast in the absence of lightness contrast (red, yellow, green, or blue on gray) were presented to subjects aged nine to adult. Contrary to Piagetian expectations, the illusion magnitudes resulting from the colored figures did not decline with age.
Evidence from various areas of investigation was cited to support the view that an aging process in the visual receptor mechanism might be expected to bring about a rise in contour detectability thresholds. Support was also garnered for the view that certain geometrical illusions which decline with chronological age are determined by the degree of figure-ground contrast (or contour strength) of their inducing lines. Two experiments were carried out, the first to measure contour detectability thresholds at 5 age levels (8 yr. to 12 yr.), and the second to measure the magnitude of a modified Mueller-Lyer illusion at these age levels. Both experiments yielded significant results in the expected directions. Correlation of the results based on common Ss yielded a significant negative r. Intelligence correlated negatively to a significant degree with contour detectability threshold, but not with magnitude of illusion. Possible implications were discussed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.