The expectancy effects of caffeine on cognitive performance

UNCW Author/Contributor (non-UNCW co-authors, if there are any, appear on document)
John E. Lothes II, Temporary EPA / Faculty (Creator)
The University of North Carolina Wilmington (UNCW )
Web Site:
Robert Hakan

Abstract: Numerous studies have been conducted on caffeine and its stimulant effects. However, studies that have been conducted to examine the effects of caffeine on alertness and memory have produced conflicting results. Several factors may be critical in explaining these mixed results, one of them being dose level. Past research has shown that performance improved with low doses of caffeine but higher doses of caffeine hindered performance on mental rotation. The purpose of the present study was to test the effects of caffeine under conditions that are better controlled than previous studies to determine its dose-related effects on a mental rotation task and a paired-word verbal memory task. Low levels of caffeine were predicted to improve performance on the Mental Rotation and Verbal Short-Term Memory tasks and higher doses to produce a decrement in performance on these tasks. “Average” caffeine consumers were recruited with a screening survey. Subjects were administered caffeine in capsules (0mg/kg, 1mg/kg, 2mg/kg & 3mg/kg in capsules or 0mg/kg or 2mg/kg caffeine in a decaffeinated cup of coffee). Procedural variables were controlled for that many past studies have failed to control for, such as caffeine dose, participant’s weight, participant’s caffeine use frequency, participant’s drug use history, time of day effects, influence that food consumption may have on caffeine, gender effects and withdrawal effects. The results showed that there were no significant differences in performance between the dose groups. But when a cup of coffee condition was added, performance for subjects given both decaffeinated coffee and caffeine coffee was significantly better, or showed a trend for better performance, on the mental rotation task and the paired-word task than did the capsule conditions. The results also agreed with past research that males performed significantly better than females on the mental rotation and that females performed better on the task of verbal memory.

Additional Information

A Thesis Submitted to the University of North Carolina at Wilmington in Partial Fulfillment of the Requirements for the Degree of Master of Arts
Language: English
Date: 2009
Behavior--Drug effects, Brain--Effect of drugs on, Caffeine--Physiological effect, Performance
Behavior -- Drug effects
Caffeine -- Physiological effect
Brain -- Effect of drugs on

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