Naming in patients with Alzheimer's disease: influence of age of acquisition and categorical effects.

The role of age of acquisition (AoA) and other variables classically supposed to influence lexical semantic tasks is explored in Alzheimer's disease (AD) patients. A naming test that included living and nonliving items was given to patients and controls. Measures of AoA of the test items were obtained from normal subjects. Living items were acquired earlier than nonliving items. Semipartial correlation analyses were performed to determine the independent contribution of each variable to naming. The "category" (living vs. nonliving items) was included as an independent factor. It emerged that AoA, name agreement and category (with living category predicting lower scores) were the main predictors of naming in AD patients. Only factor agreement reached significance in control groups. The hypothesis is discussed that the category dissociation may be produced by the different nature of the semantic correlation network that makes the categories differentially demanding of processing resources.