The experimental results show that drinking coffee after study can enhance memory.

Participants were asked to identify image targets outdoors or indoors, and five minutes later to take either a caffeine pill or a placebo pill. The researchers took saliva samples from the participants in advance to analyze their caffeine levels, and then repeated the test three hours and 24 hours later. The next day, participants were shown images that were identical, similar, and randomly selected.

Both groups of participants accurately identified new and old photos, but participants who took caffeine pills were better at spotting similar images. The researchers noted that participants who took placebo pills mistakenly thought they were original images from the previous day, suggesting that caffeine improved certain memories at least 24 hours after drinking coffee. The journal Nature Neurology published the findings.

"Caffeine helps strengthen long-term memory," said Dr. Michael Yassa of the University of California, Irvine. We have long known that caffeine enhances cognition, but its effects on memory enhancement and its role in making memory resistant to forgetting have never been studied in detail in humans. Our study is the first to show that caffeine has a specific effect on reducing forgetting after more than 24 hours."

Researchers say the brain's ability to recognize differences between two similar objects means higher levels of memory retention. Asa said: "If we used standard cognitive memory tasks without similar image targets, we found no effect of caffeine. But if you use image targets that are harder for the brain to recognize, caffeine seems to enhance memory." The study differed from earlier experiments that showed little or no effect of caffeine on long-term memory, because participants who saw the images managed to recall them only after drinking coffee.

"Almost all previous studies have linked pre-lesson coffee drinking to improved memory, but it's not clear whether this is due to caffeine's effect on attention, alertness, focus or other factors," Asa said. By analyzing caffeine experimentally, we ruled out these effects and showed whether it enhanced memory or did not." Studies have shown that taking a smaller dose of caffeine an hour before viewing an image does not improve memory.