Aging and counting speed: evidence for process-specific slowing.

The performance of adults ranging in age from 20 to 86 on two nonlexical tasks that required different types of counting operations was examined. Subproportional age effects for incrementing speed and for enumeration speed (counting 5 to 8 items) indicate that some types of counting processes are exempt from the slowing effects of aging. Increased age was associated with a diminished frequency and slowing of subitizing (counting < or = 4 items) as well as with slowing in the speed of initiating the incrementing process, but the course of age-related slowing for these measures is described by different functions. These results indicate that cognitive slowing is not equivalent for different types of processes involved in counting and numerosity judgments.