Language Acquisition in Humans
by Loretta F. Kasper, Ph.D.
from Interdisciplinary English © 1998-2003

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Stages of language acquisition:

All human babies can learn at least one language system.  Babies go through a series of stages when learning their native language.  At the first stage, cooing, all babies sound alike, no matter where they live or what their native language is.  During the second stage, the indistinctive coos take on the sounds of the vowels of the baby's native language.  At this point, the babies begin to sound differently and they are now on their way to learning to speak their specific native language.

When babies are ready to produce full words, they generally begin by producing one-word utterances consisting of nouns.  These nouns usually refer to the objects in the baby's environment.  Babies then progress to two-word utterances, usually consisting of a noun-verb combination.  As they become more advanced in first language acquisition, they produce longer utterances, consisting of three or more words.  Babies usually add adjectives to their utterances, and then finally adverbs.

Critical period for language acquisition: the case of Genie:

Scientists believe that there may be a critical period for first language acquisition.  This means that there is a time limit during which the baby must be exposed to language if he/she is to acquire language normally.  A famous case study which lends support to the critical period theory is the case of Genie.  Genie was a young girl who was locked in a small closet-like room at the age of 18 months by her schizophrenic father.  Her mother was blind and was also abused by the father, so she was unable to help Genie.  After her father died, Genie was finally freed from the closet.  She was 13 years old.

When Genie was first locked in the closet, she was just beginning to acquire language.  What kind of language skills would she have when released at the age of 13?  Genie's tragic case provides evidence that language acquisition may be limited to a critical period.  Although Genie is now an adult, her language development is quite immature.  She produces mostly nouns, some verbs, but few adjectives or adverbs.  Her utterances usually consist of no more than three words.  After intensive language training and psychotherapy, Genie has not been able to acquire normal language skills.

Why is there a critical period for learning language?  How long is that critical period?  The critical period is thought to be related to brain plasticity and lateralization.  Plasticity refers to how flexible the brain is in learning various functions.  Lateralization refers to the specializations of the two sides, or hemispheres, of the brain.  Scientists believe that the critical period for first language acquisition ends somewhere between the ages of 4 and 12.  At this age, the brain appears to lose its plasticity for learning language.  In addition, specialized language behaviors become controlled primarily by the left hemisphere of the brain.  In theory, if a child is not exposed to language during the critical period, he/she will never be able to acquire it normally.

Genie was not exposed to language during the critical period.  She was not spoken to; she did not learn how to form words and to combine those words into sentences.  When she was released from the closet at the age of 13, her brain had lost its ability to learn normal language.  However, we must remember that Genie suffered more than language deprivation during her captivity; she also suffered social deprivation.  The social deprivation probably played a role in her later language development.

Theories of how we acquire language--Chomsky versus Skinner

The linguist Noam Chomsky believed that all people had an innate knowledge of the grammar of their native language.  This means that no one had to specifically teach you the grammar of your native language; when you began speaking as an infant, you automatically produced utterances that were grammatical in your native language.  Support for this theory comes from studies of child language.  Children produce utterances in the correct word order without ever having been specifically taught what that order is.  Other scientists disagree with Chomsky's theory. 

In contrast, the psychologist B.F. Skinner believed that children must be taught all aspects of language, and that they learn the rules of their native language by imitating what they hear in their environment.  Cases such as Genie's lend some support to Skinner's theory.  Without ever having been exposed to language, Genie was unable to produce it.

How do we actually acquire language?  The process of language acquisition probably involves a little of both Chomsky's and Skinner's theories.  We might use the following analogy to illustrate: There is a light switch in our room.  All of the circuitry necessary to turn on the lights is built into the wall.  However, unless we flip the switch, the room remains dark.  So it is with language acquisition.  The circuitry for learning language is built into our brains at birth.  But, unless we are exposed to language, unless we hear the patterns of language, we will not experience normal language acquisition.

Problems in second language acquisition:

Once we have acquired a first language system, many of us go on to learn a second language.  What problems do we encounter in the process of second language acquisition? 

Learning a second language is a very difficult task for many people.  Each language contains its own system of rules for how sounds may be combined into meaningful speech patterns.  This means that words must be combined in a specific order to yield a meaningful sentence that will be understood by all people who speak that language.  It also means that meaningful patterns of word order may vary across different languages.  For example, the standard word order in English is Subject-Verb-Object (S-V-O), while it may be S-O-V in another language.

Word order rules are often troublesome for students learning a second language.  If they are to avoid mistakes when speaking or writing the second language, students must be aware that rule systems are not the same for all languages.

Students learning a second language also have difficulty with pronunciation.  The way letter combinations are pronounced varies not only across languages, but also within the same language.  This is why students learning English have a particularly difficult time with pronunciation.  Regional variations in the pronunciation of certain letter combinations are very confusing for ESL students.  An additional pronunciation difficulty results from the large number of silent letters in English.

When children learn their first language, there is no interference from any other language system.  However, once we know a language system, our knowledge of the rules of that system tends to interfere with our acquisition of the rule system of the second language.  However, we can make the process easier if we compare and contrast the rules of the new language system to those of our first language system.  This helps to make us more aware of the differences between the two languages and so minimizes the problem of first language interference.  We can become successful language learners by using our knowledge of one language to help us learn a second or even a third language.

Some research shows differences between people who learn a second language at an early age and those who learn it at a later age.  Children who grow up learning two languages may actually develop a "bilingual brain".  The brains of these "early bilinguals" appear to process language mainly through the left hemisphere while the brains of "later bilinguals" process it through the right hemisphere.