Question: Research has found that older adults, over age 65, tend to show optimal cognitive functioning (e. g., decision making, information processing, memory for words and prose) in the morning with intellectual performance declining in the late afternoon. In an article for Psychological Science, Lee Ryan, Colleen Hatfield, and Melissa Hofstetter proposed that caffeine, a simple stimulant, could ameliorate declines in memory performance late in the day. For their study, they recruited 28 individuals over age 65 who had been prescreened for neurological disorders and other factors that could impair normal intellectual functioning. The researchers also administered the Morning-Evening Questionnaire, a measure of the time of optimal daytime performance. Only people who were classified as “morning” types were retained for study. Half of the participants were tested for recall memory in the morning and the other half were tested in the afternoon. At each testing session, participants were required to drink a cup of coffee. Half of the participants drank caffeinated coffee (the experimental group), and the other half drank decaffeinated coffee (the control group). Thirty minutes after drinking the coffee, participants were asked to study a list of 16 words, and after a distraction task and a 20 minute delay, were required to recall as many words as possible.

The researchers recorded the number of words recalled correctly by each participant, and the mean scores for the four test conditions were as follows:*