Date of Award

Fall 2011

Access Type

Thesis - Open Access

Degree Name

Master of Science in Human Factors & Systems


Human Factors and Systems

Committee Chair

Shawn Doherty, Ph.D.

First Committee Member

Albert Bouquet, Ph.D.

Second Committee Member

Cass Howell, Ed.D.


Although caffeine is the most widely used drug in the world, research on the effects of caffeine on mental performance tasks (especially short term memory tasks) is inconclusive. One possible explanation for this limited understanding is the lack of studies accounting for participant expectancy surrounding caffeine. This study examined the effects of caffeine dosage (0mg, 200mg, and 400mg) and expectancy related to past caffeine use (positive, negative) on short term memory span task. A two-way Analysis of Variance showed that the two independent variables (caffeine dose and expectancy), did not significantly influence the short term memory span score. However, the interaction of caffeine dose and expectancy was found to be significant for short term memory span score. This is an interesting finding to consider in the inconclusive research area of caffeine and mental performance. It is important, therefor, for experimenters evaluating the effects of caffeine on various mental tasks to take into consideration the participant's previous experiences in using the drug as well as expectancies regarding their own performance when under the influence of caffeine. The results are examined and recommendations for future research are discussed.