All learning is state dependent.  Do you remember your high school prom or another significant event like that?  Sure you do, and I bet for a brief moment just now you went back there . . . remembering the sounds, . . .seeing the colors and . . .feeling the excitement. 
  Why did that happen?  Because you were in a 'state' at that time and your brain stored that memory, state and all.  That is why when you hear an 'oldie' you really liked, you get those same feelings and thoughts that you had years ago when you heard it, all over again.
  By now you are wondering how can you harness that state dependency learning for something really useful?  Like taking tests, duh!
  Here is a technique Janie and I teach our face to face students at Columbia College.  It is a way to go into a learning state, study, then go back into that same learning state when you need to recall.  Give it a go.  The more you do it, the better and faster you get.
The Learning State
The Learning State