Well, it has to somehow figure out you meant refrigerator before it can learn you said refrigerator; at least close enough to offer it as an option. I believe most of the learning is in Siri, where your responses offer a greater degree of feedback.
And, guessing from the many blog posts, some people's voices just don't seem to work right with Siri or Dictation. I imagine it's something that Apple will have to continue working on for the product's entire life.
Here is a quick test I did. I had no problem getting it to recognize refrigerator. It did fail on the word 'opened', but notice the blue underline and alternate interpretations it offered. I'm guessing the next time I say 'opened' it will be more likely to get it right. {providing I make the correction} To be fair, I stumbled a bit saying that word, and two previous test I made with the same sentence got it right on the first try; as well as refrigerator.
None of this is particularly helpful.
I suppose you could practice your best newscaster impression.