Contour Detectability Threshold as a Function of Chronological Age

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Abstract
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.