If you've ever wondered why our voices go up a few octaves and become distinctly sing-song-y when we talk to children (and yes, even a misanthrope like me does on occasion talk to children), Professor Steve Jones may have an answer.
And thereby hangs a tale; for rhythm is essential to language. Children pick up the pulse of speech well after they have learned its vocabulary and grammar. That explains in part why they sound childish and why adults talk to them in such an embarrassing way. The young pick up trochees first (which is why "Twinkle, twinkle, little star" - a perfect example of the form - is so popular and may even lie behind Shakespeare's use of the same rhythm for the child-like figure of Puck). An ability to respond to the ponderous iamb takes much longer to emerge. When faced with a complicated word like "banana", infants often turn it into a tasty trochee, or "nana".