The Johns Hopkins researchers conducted a double-blind trial in which participants who did not regularly eat or drink caffeinated products received either a placebo or a 200-milligram caffeine tablet five minutes after studying a series of images. Salivary samples were taken from the participants before they took the tablets to measure their caffeine levels. Samples were taken again one, three, and 24 hours afterwards.
The next day, participants were asked to identify images they had seen the day before. Some images were new, and some were similar but not exactly the same. For example, if they were shown a picture of a yellow rubber duck originally, the next day, it was a picture of a rubber duck that was shorter and thicker, says Yassa, who was at Johns Hopkins when the study was conducted but now is an assistant professor of neurobiology and behavior at the University of…
