Inclusion Criteria:  Be 65 or older Have ≥ 8 years of education Be sufficiently fluent in the English language to understand instructions and perform the neuropsychological tests (as the purpose of the project is to study healthy aging) Score above levels indicating possible cognitive impairment on the Mini Mental State Exam (MMSE) (≥ 26) Have an estimated intelligence quotient (IQ) score ≥ 90 based on the American National Reading Test (AmNART) Have a score within 2 standard deviations (SD) of the age-appropriate mean on the short form of the Boston Naming Test Have a score within 2 SD of the age-appropriate mean on the Logical Memory Subtest of the Wechsler Memory Scale-Third Edition  Exclusion Criteria:  History of Central Nervous System (CNS) diseases or major psychiatric disorders based on Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria Score of greater than 10 on the Geriatric Depression Scale Corrected visual acuity worse than 20-50 as tested by a Snellen wall chart Severe hearing disability that would interfere with their ability to participate in the experiments (e.g., to hear instructions and participate in cognitive testing) Medical conditions (e.g., heart or pulmonary disease) that would prevent them from participating in the physical exercise training program Evidence of substantial functional decline based on interview questions and completion of a questionnaire based on the Clinical Dementia Rating Scale by an informant who knows the subject well