What do psychologists call the ability to quickly revise and remember things that a person had previously learnt

Question

I am someone very far away from psychology, actually an engineering student, but I came up with this curiosity a few days ago.

To be specific, let's assume someone is learning physics. He previously took statistical mechanics course, and studied hard. About six months passed, and he still believes that his deep understanding of statistical mechanics is maintained.

But when he tries to remember the specific derivations of formulae, he encounters many obstacles. He doesn't remember the key ideas of individual derivations, but he definitely remembers how they roughly looked.

Then at a glance it looks like someone who studied statistical mechanics really hard and didn't revise for a long time doesn't have an advantage over someone who is in the middle of process of learning statistical mechanics yet isn't studying hard. They both share the fact that they don't know the details. The only difference, I would say, is that the former has enough confidence based on his experience of understanding the subject and performing well in the exams but the latter doesn't.

But it becomes a completely different story when the former starts to revise statistical mechanics. He can somehow pull out the "ancient" memories of the ways through which he made understanding possible, and without going through the entire textbooks, but by nearly skimming through them, can combine all the pieces into, and recover, one single piece of solid understanding. And it doesn't take long - the length of time needed varies, depending on the amount he has to revise, from a day to a few weeks. However it shouldn't definitely be more than a month.

Under what mechanism of psychology and neuroscience does this happen and what do psychologists call this?

Answer 1

Looks like when your friend was freshly learning the equations, he was using more of his episodic memory but as he went "used-to" with the equations, he tapped into more of semantic memory.

Lets use familiar example. When we recite something, we usually apply the episodic memory. It works much like how we searched a song "along" a tape of a cassette recorder. We had to forward/ rewind repeatedly to find the song.

We use semantic memory when we use language (or anything we learn at a depth and develop some experiene in it). Such as while reading, we instantly recognise the letter L (a shape) is linked with sound ELL or the word "CAT" indicates a mental image of a furry carnivorous animal. We do not scroll through the entire alphabet. If we compare episodic memory as a cassette system, then semantic memory is more like a modern digital file folder system, which is just "browse, click and play" type.