Effects of relatedness and number of distractors on attribute judgments in Alzheimer's disease

Participants made judgments about the relative salience of category exemplars (e.g., fruit: apple or grape) or parts (e.g., plane: wings or seats). Mildly affected Alzheimer's disease (AD) patients were as accurate but slower than normal controls, and their response times increased more for related (e.g., apple, grape, or fig) than unrelated (e.g., apple, gym, bandit) choices as the number of alternatives was increased from 2 to 3. Performance (accuracy and response times) of moderate-severely affected patients was poorer still, but number of distractors and relatedness did not interact. In combination with previous findings (e.g., M. K. Johnson, A. M. Hermann, & J. L. Bonilla, 1995), these results suggest that the reflective processes necessary for deciding among competing alternatives show disruption early in the disease process. Such processing deficits would compound any difficulties arising from a degrading semantic structure.