Date of Award
Doctor of Philosophy (PhD)
Previous research has yielded conflicting results regarding the effects of caffeine on word list recall. Erikson et al. (1985) found that caffeine impaired recall among females when words were presented at a slow rate. Arnold et al. (1988) observed a facilitory effect of caffeine on the recall, after practice, of females tested during Days 1-5 of the menstrual cycle. Research on cognitive task performance among females suggests that performance varies according to the phase of menstrual cycle. Medical research demonstrates a relationship between estrogen and caffeine metabolism. In this study, it was hypothesized that females' recall of word lists would vary with level of caffeine administered and phase of the menstrual cycle. It was further hypothesized that the performances of oral contraceptive users and non-oral contraceptive users would differ.
Two hundred and eight females were administered 0, 2, or 4 milligrams of caffeine per kilogram of body weight. Approximately half of the subjects used oral contraceptives. Subjects were tested during either Days 1-5 or Days 9-13 of the menstrual cycle. Subjects heard 13 lists of 12 words and wrote their recall immediately after hearing each list.
The proportion of words recalled from the primacy, middle, and recency portion of each list was computed. A 3(Caffeine) x 2(Pill) x 2(Phase of Cycle) x 3(Practice) x 4(Presentation Rate) x 3(Serial Position) ANOVA was performed. A dose x serial position interaction indicated that caffeine facilitated recall for words in the primacy position.
A dose x pill x phase x rate x serial position interaction was observed. Among subjects tested during Days 1-5, caffeine facilitated recall only among oral contraceptive users for words in the primacy position at the two slowest rates. Among subjects tested during Days 9-13, caffeine facilitated recall for words in the primacy position at the three slowest rates among non-oral contraceptive users and for words in the middle position at the fastest rate among oral contraceptive users.
Results suggest that among females, the effects of caffeine on word list recall are modulated according to the level of estrogen in their system.
Arnold, Mary Ellen, "The Interactive Effects of Caffeine and Estrogen on Memory for Word Lists" (1989). Theses and Dissertations. 847.