Age of Acquisition Affects Object Recognition and Naming in Patients with Alzheimer's Disease

Twenty-two patients with a diagnosis of dementia of the Alzheimer type (DAT) and a comparison group of 22 age-matched individuals took part in an object decision and picture naming task. The age of acquisition (AoA) of the picture names was manipulated (25 early, 25 late). The comparison group identified significantly more objects as real than the patients. While the comparison group made very few errors in object decision, DAT patients failed to classify significantly more late than early acquired objects as real. The patients also named significantly fewer pictures than the comparison group, showing a differential impairment in naming late acquired objects. Late acquired objects induced proportionately more visual errors in the patients than did early acquired objects. The results are discussed in terms of current theories of age of acquisition and of the impact of Alzheimer's disease on lexical and semantic processing.