How a Baby Learns to Talk: Part III

This is the third part of a Science Friday series on how a baby learns to talk.  Check out the first post here and the second post here.

    We have looked at how babies begin to babble and then say specific words.  But, how do they know in what order to put the words?  While Q-ball isn't in this stage yet, she has started combining some signs with the correct word order.  For the phrases she uses, I assume she is mirroring the phrases that I use with her.
    However, research has shown (in a fancy experiment involving Sesame Street puppets...) that toddlers between 16-to-18 months recognize the importance of word order. Specifically, they can tell the difference between phrases like "Mama is feeding Q-ball" vs. "Q-ball is feeding Mama."  This assumed understanding of word order is further verified by the fact that the vast majority of toddlers' first two word phrases are in the proper order.  Think "more banana," "I want," "get down," etc.  As was mentioned in the first post of this series, Noam Chomsky's very widely accepted theory of Universal Grammar states that all humans are innately wired to know the general form that any language takes.  In the case of word order, Chomsky's theory tells us that humans innately know structure dependence, so toddlers' correct use of word order goes above and beyond mirroring the phrases of those around them and is, instead, part of the the human brain's innate capacity of language learning. 
     Following two-word phrases, toddlers go even deeper into forming and practicing grammar rules.  Much of the research and observation on the subject of language learning  actually focuses on the mistakes and pauses that young children make as part of the learning process.  For example, as toddlers form increasingly complex sentences, they typically pause between noun and verb phrases rather than pause in the middle of a phrase. ("I want...the blue pants" vs. I want the...blue pants.")  This examples shows researchers that, as part of structure dependence, humans innately seem to know various parts of speech within a language.
    Again focusing on the mistakes that young language learners make, researchers believe that humans innately know that changes change be made to the beginning or ending of a word.  In this case, toddlers typically overregularize. So, they will add "-s" to goose, deer, and foot.  Or, they will add "-ed"  to run, do, or sit.  Scientists believe that this is a child's way of creating and applying their own language rules.
    While grammar rules vary from language to language, the two rules mentioned above (specific parts of speech and adding beginning or endings to words) are part of Universal Grammar.  As such, all children, despite their native language, have been observed making these same advances in grammar development. 

Source:

Eliot, L. (1999). What's Going on in There? Bantam Books: NY, NY.
Crain, W. (2011). Theories of Development: Concepts and Applications. Prentice Hall:Boston.