In the study, researchers examined participants' brain activity while they performed a task designed to require attention. Specifically, the researchers looked at how fast the brain responded to a change in letters appearing on a computer screen.

Before the task, participants consumed 8 ounces of either water, water with caffeine, or water containing the energy drink 5-Hour Energy. The caffeinated drinks were adjusted so that they had the same amount of caffeine per pound of participants' body weight, and all drinks were colored blue.