But I just read this at http://www.dailymontessori.com/
Speaking in high pitched tones as when they were babies "can impede in their language development in learning how to really talk. Toddlers need to be spoken to like a real person and not ‘like a dog’ anymore. They are smarter than we give them credit for and absorb everything that is said to them. This is a sensitive period for language in children so take advantage of it and model it properly.".I'm not sure if they mean simply the high-pitched tone or also speaking in 'motherese' to de widdle wums.
I definitely never spoke in fractured English, but my voice at times can reach decibels only heard by dogs ... I think I'll start using more of a normal tone with our Little Man now, except when I greet him in the morning. If you can't go high then, well there's no hope for the world.