Let me tell you about my father and his flashcards.
The Koreans have exams to get government jobs. In the United States, there is a postal exam to get a job with the US Post Office. My father was a postman. When he was studying for the exam, he would have flashcards spread all over the living room floor.
To be a postal worker requires significant memory skills. They need to learn all the postal codes plus know mail routes and be able to quickly sort mail. There are approximately 43,000 ZIP Codes in the United States. That my father could instantly recall the zip code for any place was a feat that never ceased to amaze me.