Do dictionaries make my brain operate slower? Does it make me 'stupid'?

As you may know I am Dutch, so English is my second language.
Therefore I need to use dictionaries quite often when I am writing questions and answers on Fluther.
Now, recently I have found that when I go there for a certain word and I see the translation, I go: “Ah, of course, that was not so difficult, I knew that word and had I tried a little harder I should have found it without the dictionary.”
This evening, for my previous question, words I looked up were announced and indifference.
Especially announced was way too easy, I should have been able to dug it up from my own head.
My idea is that, contrary to what I thought before (namely that dictionaries and sites like Wikipedia only broaden my knowledge and vocabulary), using these kind of sites is ‘dumbing’ me down.
Since most of you speak and write English I assume that you don’t look up words in dictionaries as often as I do, but my question to you still is:
Do dictionaries and encyclopedias make our brains work slower?
Will my vocabulary increase or decrease now that I ‘prefer’ to use these sites, rather then using my brain?
Do/did you notice something similar, for you?