Abstract reasoning in age-related neurological disease.

Subjects with a variety of neurological disorders including Alzheimer's disease (AD) were tested for abstract reasoning ability with two new tests that do not involve high-order language, memory, or visuospatial skills. All groups performed at the normal level except the patients with AD, who performed poorly on the test of logical reasoning ability, but relatively well on the test of the ability to recognize relationships between common objects. The results suggest that in AD, relational abilities may remain intact well into the disease, whereas generational abilities may be among the cognitive skills that are impaired early in the course of the disease.