Parents of newborns often hear about the importance of speaking to our babies. It’s sound advice, as far as it goes: research shows that exposing very young children to language boosts their brainpower and prepares them for later academic success.  But the guidance feels incomplete. How, exactly, should we speak to our very small children? What should we say? Does cadence matter? Tone? Worse, for parents who want desperately to give their babies a leg up, obsessive focus on language can come at the expense of other important experiences, driving exhausting and unproductive parenting practices. Fortunately, language development research adds texture to the standard advice with practical applications. The key,…