Since I have been a child the word retard has NOT been used for people with developmental disabilities, it has only ever been used to describe people who've done something incredibly stupid that they had the capacity not to do. In fact, I have worked with low and high functioning people with developmental disabilities, and one of the high function people actually told me to use the word when he's being stupid, as I was using the word goof before, and that had unfortunate prison meanings that the resident didnt like.