Age and familiarity in memory scanning.

Sixty-five healthy males (31 to 75 years old) memorized lists of six letters (familiar or unfamiliar organization). Letters were then presented singly, and subjects responded yes or no according to whether a given letter was in the memorized set. Subjects of all ages took longer to respond in the case of the unfamiliar list. This was disproportionately true for the oldest subjects, consistent with the idea that the age-related differences in the unfamiliar condition could not be wholly accounted for by psychomotor factors. The distributions of response latencies in the oldest groups had greater variance and skew.