Caffeine has a weird relationship with memory: it can hurt our ability to remember, but it can actually enhance our ability to recall.
So how's it work?
About 90% of Americans ingest caffeine daily. We often drink coffee in an attempt to make ourselves feel more awake. In this way, caffeine acts as an enabler; it aids and abets us in the crime of not getting enough sleep.
If you are going to recall the events of the day, you need to weave them into your memories, through a process sleep scientists call consolidation. But you only get into consolidation mode when you're in the deepest levels of sleep. So the less sleep you get, the less of an opportunity your fresh experiences have to consolidate into your longer memories.
We can infer, then, that you're doing damage to memory if you use caffeine as a shortcut around slumber.
Yet caffeine can also bolster your ability to recall, as a new study from Johns Hopkins University suggests. We'll let neuroscience professor Michael Yassa explain:
To see how caffeine affected people's memory, Yassa's team asked people to look at everyday images: a rubber duck, an office chair, a saxophone. Then half of the subjects got a dose of caffeine. Then, a day later, they were shown a mix of images: some were the same as the day before, some slightly different, others completely new.
The people who took the caffeine were better able to identify which objects were similar but not identical than the placebo group.
"If we used a standard recognition memory task without these tricky similar items, we would have found no effect of caffeine," Yassa said in a statement. "However, using these items requires the brain to make a more difficult discrimination—what we call pattern separation, which seems to be the process that is enhanced by caffeine in our case."
The study even sorted out the optimal dosage for getting that enhancement: about 200 milligrams, which you'll find in a strong cup of coffee. More than that and folks start getting headaches, nausea, and other side effects you'd rather forget. Less than that and you don't get the benefits.
Hat tip: the Atlantic