How did you learn to speak your native language? Notice that this shouldn't be such a puzzling question. We often ask questions such as, do you remember when you learned to tie your shoes, ride a bike, and eat with a fork? Sometimes we can remember because a parent helped us learn how to do these things.

Now, since we always speak the language of our parents, they must have helped us learn to speak our first language. But do you remember when your mother taught you the past tense? When your father laid down the rules for passive sentences? We don't remember these important moments of our childhood because they never occurred.

Our parents didn't teach us how to walk and they didn't teach us how to talk. Yet we learned from them. How can this be? Certainly there must have been a subtle, perhaps intuitive teaching process that neither our parents nor we were aware of. We begin by imitating what we hear our parents say as best we can, repeating random phrases. Our parents in subtle ways punish us for the childish speech errors we make (by not responding, correcting the error, etc.) and reward correct phrases (by responding positively). As our speech improves, our parents respond more positively and less negatively. No?

First, let's examine the assumption that children begin speaking by trying to repeat what they have heard their parents say. Have you ever heard a child say things like this:

Daddy go

He hitted me!

No eat cake

Who did they hear utter such phrases? "Daddy go" is an attempt to express 'Daddy is going'. But if the child were merely trying to repeat this common phrase, choosing random two-word combinations, he or she would also occasionally say "Daddy is" or simply "is going"? Yet these two phrases do not occur as normal speech errors of children while "Daddy go" is a common one.

Second, research shows that while mothers often respond to the semantic content of what their children say ("No, that's not a doggie; it's a cow"), they very rarely respond to the grammatical status of their children's phrases. Indeed, when parents do respond to speech errors, they most often respond positively. Here are a few advanced errors from the history of my family. What do you think our response was—correction or laughter (which I take to be a positive response)?

Mama, mama, there's a tree-knocker in the back yard!

It's raining, where is the underbrella?

Give me the beach-lookers! (binoculars)

In fact, parents themselves make grammatical errors when they speak. Despite the fact that children don't know when their parents are speaking grammatically and when they are making errors, all children grow up knowing (if not always speaking) the language perfectly.

So how do we learn to speak? Recall the example above, "He hitted me." Although hitted is not a word children hear adults utter, it is wrong for an interesting reason: the verb, in a sense, has the "right" ending on it for the past tense. In other words, the only way a child learning language could make such an error is that he or she is learning a rule that derives past tense verbs from verb stems. What the child hasn't mastered at this stage is the exceptions to the rule. Still, it shows that children look for and learn grammatical rules from nothing more than the utterances they hear.

Notice also that the words in the erroneous phrases are all in the correct order. No child would say "go Daddy" for "Daddy is going" or "cookie mommy" for "Mommy's cookie". By the time a child begins putting two words together, he or she has already mastered the basic rules of syntax and applies them correctly even in their erroneous speech. It takes the child a little longer to master the rules of morphology, i.e. affixes and suffixes.

The evidence then indicates that children do, in fact, absorb a massive number of sentences and phrases but rather than parrot them back, they abstract rules from them and create their own grammar which they then apply to create new utterances they have never heard before. Over the years from 2-6, when language is mastered, children constantly adjust their grammar until it matches that of the adult speaker population.

This critical period between the ages of 2-6 suggests that first language learning, like walking, is an innate capacity of human beings triggered by a level of development more than feedback from the environment. That is, so long as a child hears a language–any language–when they reach this critical period they will learn it perfectly. If this is true, any child not hearing language during this period not only should not learn to speak but also should not be able to learn to speak. The ethical implications of research on this question are obvious. However, there have been a few tragic non-scientific bits of evidence that supports the innateness + critical period hypothesis.

The first bit of evidence comes from the so-called Wild Boy of Aveyron, Victor. Victor is the name given to a boy found roaming the woods of Averyon in southern France toward the end of September 1799. He behaved like a wild animal and gave all indications that he had been raised by wild animals, eating off the floor, making canine noises, disliking baths and clothes. He also could not speak. He was taken in by Doctor Jean Marc Itard who had developed a reputation for teaching the deaf to speak. However, after years of work, Itard failed to teach Victor to more than a few basic words without correct endings, the indicators of grammar.

A similar event unfolded in Los Angeles in November 1970 when a 13-year-old girl was discovered who had been isolated in a baby crib most of her life and never spoken to. She was physically immature, but had difficulty walking and could not speak. Psychologists at UCLA spent years trying to teach "Genie" (as they called her to protect her identity) to speak. While Genie did get to the point where she could communicate, her speech never advanced beyond the kind of constructions we saw in the first set of examples above, the point where the language explosion in normal children begins. In other words, she could use words to the same extent as chimpanzees but could not manipulate grammar, as indicated in the prefixes, suffixes and 'function' words missing in the first set of examples above. At middle age she stopped talking altogether and was soon committed to a mental institution.

The evidence is not conclusive but, such as it is, it suggests that language is an innate capacity of human beings which is acquired during a critical period between 2-6. After that period, it becomes increasingly more difficult for humans to learn languages.

Remember, the magic word is linguistics, a relatively new science. Language acquisition is a subfield of the very active field of psycholinguistics, another of the many interdisciplinary areas of linguistics. Check the Linguistics Program listings at the university nearest you for what you can take next semester.