Memory retrieval is easier when the context of recall matches the context when the memory was formed. If you learn the content underwater, you will remember the content better when tested underwater than on the beach.
Paper: Context-dependent memory in two natural environments: on land or underwater
This is one of my favorite studies on memory (because it's quite funny, lol).
The researchers asked half of the participants to memorize a list of unrelated words while diving twenty feet underwater and the other half to memorize the same list on the beach. Later, they test these participants to recall these words underwater or on the beach. So essentially, there are four groups:
- Learned the content UNDERWATER and recalled it UNDERWATER
- Learned the content UNDERWATER and recalled it ON THE BEACH
- Learned the content ON THE BEACH and recalled it ON THE BEACH
- Learned the content ON THE BEACH and recalled it UNDERWATER
They found that if divers learned the words underwater, they remembered more words if tested underwater than on the beach. Likewise, if divers learned the words on the beach, they tested better on the beach than underwater. In other words, they can recall more when the test conditions match the learning conditions.
This context dependency is true for other kinds of memory too. No matter whether it's prospective memories (what you plan to do), episodic memories (what happened), semantic memories (information you know), or muscle memories (how to do things), memory retrieval is easier when the context of recall matches the context when the memory was formed.
Moreover, this context dependency isn't only about the environment. As I noted in Mood and Memory Recall, a sad mood can make sad memories easier to recall. Our emotion is part of the context.
This also relates to why changing study environments can significantly improve how well you remember information. If you want to recall a piece of information better anytime, anywhere, you should try to encode that memory with multiple different contexts, similar to how dual-encoding theory works.