My dd5 too. When asked what he wants to be when he grows up-- a man! Will never dress up for Halloween. He is better now and uses "expressions", but he always has to follow up his statement by saying, "that's just an expression".
I expect they outgrow it over time as they learn deeper vocab usage and nuance...and I imagine every kid has a slightly different starting point and ending point, but mine did seem to start out more literal than other kids. He didn't want to be anything for Halloween, because he didn't want to turn into that thing. I always thought it was interesting...but the more I think about it, the more it makes sense. Why wouldn't we say just what we mean?
