A study out of Carnegie Mellon University showed that "motherese" helps children learn language faster.
“Motherese,” aka “parentese,” aka “infant directed speech” is a universal language. You are already familiar with this language, as you have that natural ability to use it in those first few months of life to talk with your baby.
Studies have shown that no matter what language is being used, motherese carries the same characteristics. It has a certain musicality to it. It is slower, the vowels are longer, the consonants shorter, the words are simpler, and the pitch is higher. There are fewer syllables per phrase, making it easier and more interesting for our little ones to listen and learn.
Here’s what is sounds like:
As babies’ awareness of language and speech sounds increases, it gives them a greater foundation for developing these skills. They listen and attend to our use of this musical way of speaking, loaded with vowels and sing-songy intonation... and the first sounds they make often sound like motherese. Cooing is the first milestone reached in speech and language production, and its no wonder, since our babies have been listening to all of these vowel productions from day one.
Linguists have found that regardless of the language you speak, motherese is being used around the world. Whether you are speaking English, Mandarin, Japanese, German, or Spanish... we are all teaching our babies to talk in the same way.
It is so natural to us, that I even witnessed my 2 year old niece use this same musical voice when talking to her baby brother.
As your child begins to coo and babble and especially as they begin to say words, as they approach the 12 month mark, using motherese is no longer necessary. You want to use a more “adult-like” way of speaking so they can transition into learning how to use new sounds, with more complex use of consonants.