Design
This trial had a within-subjects 3 × 7 design: treatment (modafinil, caffeine,
placebo) × time (Overview of study design and data collection. All study days were
identical, the only difference being the medication administered
(modafinil 200 mg, caffeine 300 mg, or placebo).A wash-out period of at least 7 days was implemented to ensure that the
investigational products were completely eliminated and would not interfere on
subsequent trial days.The study was double-blinded as both the subjects and investigators were unaware
of the treatment given on test days. The order of the treatments for each
individual subject (placebo, caffeine, or modafinil) was based on a
computer-generated randomization schedule organized and monitored by an external
statistician. Randomization was performed using all possible (six) treatment
sequences to ensure balance for carryover effects, that is, improving skills or
learning bias on the test battery. For every test day the researchers received a
treatment kit from the pharmacist. The treatment kits were labeled with the
subject number and the test day and contained identical capsules.