found that participants who had been given caffeine pills had better memory recall. Scientists studied 160 participants ages 18 to 30, and showed them various photos of items at the outset, asking study subjects to classify the items as “indoor” or “outdoor.” Half the participants were given a 200 mg of caffeine in the form of a pill
after that classification, the other half a placebo. One day later, all the participants were shown the same pictures, as well as some they hadn’t seen before. They were asked whether each photo was new, old or similar to the originals.