The effects of aging on cognitive function were investigated. Cognitive tests were given to subjects in various age groups to define changes in cognitive functioning due to age. A color word test, a memory scanning test, a digit span test, and a continuous recognition for numbers test were administered. In children and young adults, performance on the word color test increased with age due to decreased perceptual operating time; however, perceptual operating time increased in subjects over 65. Younger subjects performed better on the memory scanning test. Digit span results for average ages of 22.7, 39.6, and 76.6 years were 7.3, 7.6, and 6.1, respectively, indicating that digit span decreased significantly with age, but the change was not apparent until around age 60. For the continuous recognition test, the same subjects had sensitivities of 1.13, 1.07, and 0.411 for young, middle, and old subjects, respectively. The author concludes that performance on all four tests decreases with age. The ages at which the changes take place are not clear cut or consistent; however, decrements occur during or after age 60.