Date of Award


Document Type


Degree Name

Doctor of Philosophy (PhD)




Hydrocortisone has frequently been hypothesized to increase arousal. This hypothesis was primarily based on the findings of increased adrenal size in animals who had been exposed to stressful conditions and the enhancement or impairment in cognitive abilities of humans depending on dose. There has been a lack of studies directly looking at the arousal hypothesis of the effects of hydrocortisone. The purpose of this study was to directly assess the effects of hydrocortisone on levels of arousal by manipulating both state and trait arousal. This study used caffeine as a comparison drug that alters state arousal because of its widely accepted arousing properties. Subjects were also separated according to trait arousal using the Eysenck Personality Inventory-Impulsivity Subscale.

One hundred and twenty male college students were used as subjects. As was mentioned above, the subjects were divided according to their level of trait arousal. The doses used for this study were 5 mg of hydrocortisone, 40 mg of hydrocortisone, 2 mg/kg of caffeine, and a placebo. Thirty minutes after the ingestion of the hydrocortisone, caffeine, or placebo, the subjects heard 8 word lists, each containing 12 words. Four lists were heard at a slow rate and four lists at a fast rate. Subjects heard one list at a time, followed immediately by a written recall test. Subjects' recall was again tested 60, 90, 120, and 150 minutes post ingestion.

The proportion of words recalled from the primacy, middle, and recency portion of each list was computed. A 4 (Treatment) x 2 (Impulsivity) x 4 (Practice) x 2 (Rate) x 3 (Serial Position) mixed ANOVA was conducted on the immediate recall data. A 4 (Treatment) x 2 (Impulsivity) x 4 (Delay Interval) x 3 (Serial Position) mixed ANOVA was computed on the delayed recall data.

A treatment by impulsivity interaction and a treatment by rate interaction were found with the immediate recall data. The 40 mg dose of hydrocortisone impaired high impulsive subjects' performance while caffeine enhanced low impulsive subjects' performance. High impulsive subjects recalled more words than low impulsive subjects in the placebo condition. The 40 mg dose of hydrocortisone impaired subjects' performance at the slow rate of presentation and caffeine facilitated recall at the fast rate of presentation. In addition, a marginal main effect of treatment was found with the delay data such that caffeine facilitated recall and the 40 mg dose of hydrocortisone impaired recall. The results were discussed with regard to their fit to an arousal model.

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