How does the FBI learn languages so fast?

How does the FBI learn languages so fast? Not with a secret method. Agents who need a language go through full-time government immersion training, mainly the Foreign Service Institute and the Defense Language Institute, studying five to seven hours a day in small groups with expert instructors for months on end. The "secret" is the hours. Nobody outside those programmes learns that quickly, because almost nobody else can spend a working day, every day, on nothing but the language.

What the training actually looks like

The Foreign Service Institute, which trains US diplomats, groups languages by how far they sit from English and publishes the hours each one takes. A language close to English (French, Spanish, Portuguese, Italian) needs roughly 600 to 750 class hours to reach solid professional-level speaking and reading. Distant ones like Arabic, Mandarin, Japanese and Korean run to about 2,200. Classes are tiny, often three or four students to one instructor, five days a week. That's the whole trick: a huge number of intensive hours, not a technique you can buy.

The useful takeaway for the rest of us is the ingredients, not the schedule: high-frequency words first, input you can almost follow every day, and constant speaking. You can run the same recipe in ten minutes a day. It just takes longer than a government immersion course.

Source: US Department of State, Foreign Service Institute language training.