Lexical, Sublexical, and Implicit Memory Processes in Healthy Young and Healthy Older Adults and in Individuals With Dementia of the Alzheimer Type

Five groups of participants—healthy young, healthy young-old, healthy old-old, very mildly demented, and mildly demented individuals of the Alzheimer type (DAT)—participated in a 2-phase experiment that entailed a rhyme judgment task followed by a lexical decision task, in which half of the stimuli were earlier presented in the rhyme judgment task. The results of the rhyme task indicated that healthy young and older adults did not produce an influence of word frequency on rhyme decisions. However, the 2 groups of DAT individuals produced large word-frequency effects primarily for the nonrhyming pairs. The results of the lexical decision task indicated that (a) repetition facilitated lexical decisions to words, whereas there was evidence of inhibition for nonwords; and (b) there was an increasing influence of word frequency across the 5 groups of participants. The results are interpreted with respect to attentional control of appropriate (lexical and sublexical) processing pathways and the nature of processes that are disrupted and those that remain uninfluenced in healthy aging and DAT.