Several weeks ago, I wrote about the CDC revisions to its developmental milestones. You can read the original post here. I got a lot of responses. One piece of this was people wanting more on topics like crawling, or receptive language development. I’ve got those on the list for future posts. But a large share of the responses focused on the expressive-language milestones, and in particular the issue of “50 words at 30 months.”  

Is this the right milestone, and what does it mean? I collected feedback from Michael Frank, who runs the Wordbank that I referenced in the post; from some of the speech-language pathologists behind The Informed SLP (JoAnne Berns, Marie Bloem, Katherine Sanchez, and Karen Evans); and from the CDC authors of the journal article that informed these guidelines. Today I’m going to relay and try to organize some of that feedback. I do not think we’ll get to an answer that satisfies anyone, but I’m hoping to capture the tenor of the debate. 

I’m going to start by going through a few general points of criticism, then provide the CDC response, and try to summarize.