Learned underwater, best recalled underwater

In 1975, psychologists Godden and Baddeley ran an experiment with divers. They asked them to learn word lists in two settings: on dry land and underwater, several metres down. Then they tested them in one of the two environments.

The result was clear-cut: they remembered the words far better when the place of the test matched the place where they'd learned them. What was studied underwater came back better underwater; what was learned on land, on land.

It's called context-dependent memory. Without meaning to, your brain stores cues from the surroundings —smells, sounds, place— and later uses them as keys to unlock the memory.

Hence a genuine exam trick: study in conditions similar to the test. And if you freeze, mentally recreating where you learned something can hand back what you thought was lost.