4 TO 10 MILLISECONDS PER YEAR - AGE-RELATED SLOWING OF VISUAL WORD IDENTIFICATION

This experiment examined the age-related slowing of visual word identification. Each of 108 subjects between 20 and 78 years of age performed a word/nonword discrimination (lexical decision) task in which the target was preceded by a single-word prime. Several aspects of the data were consistent with a generalized slowing model: There was a positive correlation between age and mean reaction time, the absolute magnitude of age differences increased as a function of task complexity, and the statistical control of a relatively task-independent index of processing speed attenuated the age-related variance in mean reaction time. The degree of age-related slowing was more pronounced for visually degraded targets (10 msec per year) than for intact targets (4 msec per year). Other aspects of lexical decision performance, however, suggested that some components of word identification, especially those involved in semantic activation, are relatively exempt from age-related slowing.