On the discrimination between global and local trend hypotheses of life-span changes in processing speed

Meta-analyses of age effects on processing speed suggest a single, global mechanism underlying developmental speeding and slowing in the erderly. Myerson, Hale, Wagstaff, Poon and Smith (1990) proposed an information loss model assuming that a constant amount of information is lost at each processing step in all age groups whereas the rate of information loss differs between age groups. In this study, a series of simulations has been conducted comparing global versus local information loss. This has been done for both deterministic and stochastic varieties of the information loss model. The outcomes of these comparisons were consistently negative; the information loss model fails to discriminate between global and local age effects on the reaction process. The simulations were followed by a discussion of Hohle's (1967) scheme for investigating selective age effects on processing speed. It was concluded that the combined approach of stage and distribution analysis of the reaction process augmented with psychophysiological time markers provides a powerful tool for the study of life-span changes in processing speed.