If you have trouble remembering where you parked the car, you might consider making a double shot espresso part of your daily routine.
A new study in the journal Nature Neuroscience suggests that the same amount of caffeine you'd find in a grande latte can enhance long-term memory in humans.
"We report for the first time a specific effect of caffeine on reducing forgetting over 24 hours," Michael Yassa, a professor of brain science who recently moved his lab from Johns Hopkins University to the University of California-Irvine, said in a statement.
To test how caffeine affects memory in the human brain, researchers at Yassa's lab at Johns Hopkins recruited 60 people who have a relatively low daily caffeine intake. Subjects were asked to look at 200 pictures of everyday objects like a chair, or a coffee mug on a screen and tell the researchers whether the object was an indoor item or outdoor item.
"It didn't matter what they said; we just wanted them to pay attention to the pictures," said Yassa.
Five minutes after the volunteers completed the task, half of them were given 200 milligrams of caffeine in the form of two small pills. The other half were given two placebo pills that looked exactly the same. The study was double blind, so neither the subjects nor the researchers knew who got the caffeine pills and who got the placebos.
The next day, the subjects were asked to look at another set of images and identify which pictures they had seen the day before, which pictures were new, and which pictures were similar, but a little different to the ones they had already seen. For example, maybe a coffee cup that was a different color, or a chair photographed from a different angle.
While both groups had the same success rate when it came to identifying pictures that were the same and pictures that were different, the volunteers who received the caffeine pills were better at remembering that a picture was similar, but a little different to one they had seen before.
"It is a much more detailed memory," said Yassa. "If all they remembered was 'coffee mug,' they would say the picture was the same. But they were remembering the exact coffee mug they saw."
Scientists call this type of memory — when we can determine that something is similar but not exactly the same as something we've seen or done before — "pattern separation memory." It is the type of memory we use at the end of a work day when we remember where we parked our car in the morning, rather than yesterday morning, or the morning before.
To see if more caffeine lead to better memory boosts, the researchers tried the trial again with 300 milligrams of caffeine. The results were about the same as with the 200 milligram dose, and some of the test subjects reported some uncomfortable side effects from the increased caffeine levels, including nausea and jitters.
Yassa said that there is no magic in taking caffeine five minutes after something that occurs that you need to remember. "Before or between or after or during, it would all work," he said. "The only thing I would say is: Don't drink caffeine to pull an all-nighter. Sleep is really good for memory, but if you are going to drink coffee to stay up, you won't get the boost from either one."
The next step for Yassa and his team is to figure out why caffeine helps with pattern separation memory. One potential explanation is that caffeine increases arousal levels, which can be associated with better memory.
"Other scientists have found that when animals are shocked or scared or stimulated in some way they have better memory," Yassa told the Los Angeles Times. "We know that with caffeine your heart rate can go up and there is jitteriness, and other symptoms of arousal too. Maybe these moderate doses of caffeine can boost our memory without these other side effects."