The team conducted further experiments using 100 mg and 300 mg doses of caffeine. They found that performance was better after the 200 mg dose, compared with the 100 mg dose, but there was no improvement after the 300 mg of caffeine, compared with 200 mg.
"Thus, we conclude that a dose of at least 200 mg is required to observe the enhancing effect of caffeine on consolidation of memory," the study authors write.