Learning language: How babies learn to speak

Almost all human beings acquire a language (and sometimes more than one), to the level of native competency, before age 5.

How do children accomplish this remarkable feat in such a short amount of time? Which aspects of language acquisition are biologically programmed into the human brain, and which are based on experience? Do adults learn language differently from children?

by Nicole Mahoney

Researchers have long debated the answers to these questions, but there is one thing they agree on: language acquisition is a complex process.

Most researchers agree that children acquire language through interplay of biology and environmental factors. A challenge for linguists is to figure out how nature and nurture come together to influence language learning.

Emphasis on nature

Some researchers theorize that children are born with an innate biological “device” for understanding the principles and organization common to all languages. According to this theory, the brain’s “language module” gets programmed to follow the specific grammar of the language a child is exposed to early in life. Yet the language rules and grammar children use in their speech often exceed the input to which they are exposed. What accounts for this discrepancy?

Learning language: How babies learn to speakThat is where the theory of universal grammar comes in. This theory posits that all languages have the same basic structural foundation. While children are not genetically “hard-wired” to speak a particular language like Dutch or Japanese, universal grammar lets them learn the rules and patterns of these languages — including those they were never explicitly taught.

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Some linguists believe that universal grammar and its interaction with the rest of the brain is the design mechanism that allows children to become fluent in any language during the first few years of life. In fact, childhood may be a critical period for the acquisition of language capabilities.

Some scientists claim that if a person does not acquire any language before the teenage years, they will never do so in a functional sense. Children may also have a heightened ability, compared to adults, to learn second languages — especially in natural settings. Adults, however, may have some advantages in the conscious study of a second language in a classroom setting.

Emphasis on experience and usage

Not all linguists believe that the innate capacities are most important in language learning. Some researchers place greater emphasis on the influence of usage and experience in language acquisition. They argue that adults play an important role in language acquisition by speaking to children — often in a slow, grammatical and repetitious way.

In turn, babies learn to speak by discerning patterns in the language and experiment with speech gradually — uttering single words at first and eventually stringing them together to construct abstract expressions. At first glance, this may seem reminiscent of how language is traditionally taught in classrooms. But most scientists think children and adults learn language differently.

While they may not do it as quickly and easily as children seem to, adults can learn to speak new languages proficiently. However, few would be mistaken for a native speaker of the non-native tongue. Childhood may be a critical period for mastering certain aspects of language such as proper pronunciation. What factors account for the different language learning capabilities of adults and children? Researchers suggest accumulated experience and knowledge could change the brain over time, altering the way language information is organized and/or processed.

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Why further study is needed on how babies learn to speak

While our understanding of language acquisition is incomplete, this pursuit is well worth the effort, according to NSF program officer Joan Maling.

“We still don’t understand how a child learns its first language, why some children have language disorders or how children and adults learn a second language,” she says. “And we still don’t understand what happens when a stroke or a disease such as Alzheimer’s seems to wipe out a person’s knowledge of language.”

Unraveling the process of language acquisition promises not only to help scientists answer these questions, but to explain fundamental features of learning and the human brain.

No nonsense: Babies recognize syllables

Babies are born into a world buzzing with new noises. How do they interpret sounds and make sense of what they hear? University of Wisconsin, Madison, researcher Jenny Saffran strives to answer these types of questions by studying the learning abilities “that babies bring to the table” for language acquisition. “Studying learning gives us the chance to see the links between nature and nurture,” says Saffran.

One thing babies must learn about language is where words begin and end in a fluid stream of speech. This isn’t an easy task because the spaces we perceive between words in sentences are obvious only if we are familiar with the language being spoken. It is difficult to recognize word boundaries in foreign speech. Yet according to Saffran, by seven or eight months of age, babies can pluck words out of sentences.

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In her studies, Saffran introduced babies to a simple nonsense language of made-up, two-syllable words spoken in a stream of monotone speech. There are no pauses between the “words,” but the syllables are presented in a particular order. If the babies recognize the pattern, they can use it to identify word boundaries in subsequent experiments. To test this, Saffran plays new strings of speech where only some parts fit the previous pattern, then records how long the babies pay attention to the familiar versus novel “words.” Since babies consistently pay attention to unfamiliar sounds for longer periods than to familiar ones, a difference in attention times indicates what the babies learned from their initial exposure to the nonsense language.

Saffran’s research suggests babies readily identify patterns in speech and can even evaluate the statistical probability that a string of sounds represents a word. Her research reveals the sophisticated learning capabilities involved in language acquisition and demonstrates how these skills evolve as an infant matures.

For details about Saffran’s research and experimental methods, click here.

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