Contour Detectability Threshold as a Function of Chronological 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 S s 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.