I may be misunderstanding as well, but my understanding is that children generally begin talking by using nouns and only later progress to verbs. From what I know, a general term like "that" is fairly commonly used by young children to represent virtually everything until they learn the names for everything. Also, I believe that the Dolch sight words are listed in order of how often they appear in literature and that children's literature (in particular beginner readers) try to limit their content to mostly these most common words so that children will more easily develop a sense of mastery when reading. It makes sense to me that this list would be similar to the most commonly spoken words. IS that what you are asking about?
