The polyglot spot has a great post recently, entitled So Many Questions…, discussing the value of learning question words. The verdict: You are going to use them. A lot. Definitely take the time to learn them early on.
I saw this and immediately thought of another benefit in some languages. In Hungarian, the answer to a question will often mirror the question word used fairly directly. In other words, paying attention to the suffix used in the question word helps you choose the right suffix to construct your answer.
For example, if I wanted to ask who you went to the movies with last night, I would say
Kivel ment a moziba tegnap esten?
In this sentence, kivel translates to “with who(m)”. To answer this question, the person responding will also have to use the suffix -val/vel (depending on vowel harmony) to indicate “with”, in this case appending it to the name of the person.
Edinaval ment a moziba.
“I went to the movies with Edina.” The question word indicated exactly which case ending would be needed to answer the question. Helpful, right?
Look at another example:
Mikor a koncert?
The question here is “When (lit., at what time) is the concert?”
“At eight.” To be more clear for our purposes, this could also be written as 8-kor.
This doesn’t work for every question and answer in Hungarian, but it does work more than enough to make it useful. And lets face it, when you’re trying to choose the correct ending from among 17 different noun cases on the fly, every little bit helps.