The fate of global precedence with age.

The literature is virtually devoid of studies examining the effect of aging on the "global precedence" effect (Navon, D. [1977]. Cognitive Psychology, 9, 353-383). In this paradigm, global letters formed with local letters are shown, and the subject has to recognize either the local or the global letters. The relation between the global and the local letters is either congruent, neutral, or conflicting. Five experiments are reported, with five sets of 16 young and five sets of 16 elderly, healthy, adult subjects. The global precedence effect was observed in both age groups in the basic perceptual experiment as designed by Navon (Experiment 1). In addition, young and elderly subjects were able to process separately the global and the local shapes when attention was not directed towards a specific level (Experiment 1a). However, subpopulations emerged, especially in the elderly, depending on their ability to "resist" to the interference of the global shape upon the processing of the local form. This could support the few indirect published data suggesting that global precedence tends to diminish or to disappear with age. In experiments 2 and 2a, subjects were retained only if they did process the local level better than at random. Global precedence was confirmed in both young and elderly subjects. Again, elderly subjects manifested an increased sensitivity to interference. Moreover, a general effect of age remained, even in the control (neutral) conditions, suggesting difficulties of encoding in elderly. Therefore, in Experiment 3, encoding conditions of both age groups were equated by increasing exposure duration of the material for elderly. Subjects of Experiment 3 were also submitted to a Stroop test, to verify whether the increased sensitivity to interference in the elderly was specific to the "Navon task" or the expression of a general effect of aging on inhibition mechanisms. The global precedence phenomenon was observed in young and elderly subjects, with no sign of an effect of age under these conditions; in elderly, furthermore, the interference effect did not appear to result from a general aspecific deficit of inhibition mechanisms. It thus appears that the global precedence phenomenon resists well the effects of aging, but that subpopulations of elderly subjects should be considered in future studies.