Deb that question we briefly discussed at the workshop and that you posted as a comment got this response from Jennifer:
Ben, I just came across this study that nouns and verbs are learned in different parts of the brain. I was just reading a post on your blog wondering why despite multiple reps, some words seemed to “stick” better than others. This might be why 🙂
http://www.livescience.com/culture/brain-noun-verb-learn-100225.html
Jennifer