The next time you want to remember where your keys are, put them down and then have a friend leap out of a dark corner and scare the living daylights out of you. A new experiment detailed in PNAS on Monday shows that memory of inconsequential events is improved significantly when they happen around the same time as a novel, exciting, or surprising one, though so far the effectiveness has only been demonstrated over periods of 24 hours.

In the experiment, a group of scientists taught rats to find food in a particular location. After the rats found the food, the researchers subjected them to different kinds and levels of "rewards" in the form of chemical injections to their brains, such as dopamine. The rewards were distributed some time after the food-finding event, to make sure the rats registered them as unrelated occurrences.

The scientists found that chemical surges in the brain, like the ones that naturally result from a surprising event, helped the rats remember where they had previously found food up to 24 hours before. Without them, or with chemicals that diminished memory, the rats usually forgot where the food had been by the time the next day rolled around.

The authors are uncertain what it is about surprises that make surrounding events more memorable, even if they are unrelated and mundane. They suggest that such memory persists for humans beyond the tested 24-hour period, such as when people remember where they were on 9/11 or when Kennedy was shot (but I date myself). Because of this, it might be wise to have the manservant who normally frightens away your hiccups surprise you into remembering things, too.

PNAS, 2010. DOI: 10.1073/pnas.1008638107 (About DOIs).