This is most obvious when learning a second language. If you're eg an English speaker learning German vocabulary, you soon notice that you can look at the German words and know what they mean quite easily, but the other way round is significantly more difficult.
After learning some vocab you learn that it's barely ever worth the time to even study German->English as English->German is "real" learning while the former just makes you feel like you are.
True, generating in new language is the more difficult task. The recognition part is just as important thought. To be able to verify that your own generated output is correct you need to be able to comprehend it.
After learning some vocab you learn that it's barely ever worth the time to even study German->English as English->German is "real" learning while the former just makes you feel like you are.