Age differences in the speed of cognitive operations: resolution of inconsistent findings.

Gaylord and Marsh (1975) and Cerella et al. (1981) found that the speed of cognitive operations in the mental rotation paradigm was significantly slower for groups of older adults with mean ages of 68 and 73 years than for groups of younger adults. Jacewicz and Hartley (1979) found no difference between a group of adults with a mean age of 56 and a group of younger adults. The present study included a group of younger adults, a late-middle age group with a mean age of 56, as well as an older group with a mean age of 74. The results replicated both those reported by Jacewicz and Hartley (1979) and those reported by Gaylord and Marsh (1975) and Cerella et al. (1981). They are consistent with a hypothesis of generalized central nervous system slowing, but they show that the slowing does not begin to affect performance until the sixth decade of life.