Scientists Learn More about the Evolution and Acquisition of Human Language

Overview

Of all of the behaviors that human beings engage in, probably none is so complex and yet so commonplace as speaking and listening to language. Human language is what makes communication with others possible and gives order to our physical and social environments. The question, however, of how language is acquired by children has been and continues to be an interesting and lively debate. The inquiry into how much of language is present at birth is far from settled. Research is transforming traditional views of how language may have evolved, how the human brain works, and how children acquire language.

Background

Attempting to reconstruct the evolution of human language has been extremely difficult. Whereas the physical remains of our ancestors have endured for millions of years, we have no record of early speech. Anthropologists hypothesize that human beings as we know them have existed for only 100,000 years, but the earliest written records are barely 6,000 years old. These records appear so late in the history of the development of language that they provide no clue at all as to the origin of verbal language. The language or languages spoken by our earliest ancestors are irretrievably lost.

The idea that language was divinely bestowed upon humankind is found in myth and religion throughout the world. In the Judeo-Christian heritage, God gave Adam the power to name all things. In Egypt the creator of speech was the god Thoth. The Babylonians believed language was given by the god Nabu. In the Hindu creation story, the goddess Sarasvasti gave language to the people.

The assumption of the divine origin of language stimulated "experiments" in which children were isolated in the belief that their first words would reveal an original language. The Egyptian Pharaoh Psammetichus, James IV of Scotland, the Holy Roman Emperor Frederick II, and German J. G Becanus all conducted experiments to determine an "original language." All were unsuccessful.

Other early theories suggested that language is a human invention. The early Greeks believed that a "legislator" gave the true names of things. The naturalists argued that there was a natural connection between the forms of language and the essence of things. In other words, language may have begun as a vocalization of the sounds heard by early humans in their environment.

Later, evolutionary theories would oppose the divine-origin and the invention theory of human language. Charles Darwin's (1809-1882) theory of natural selection, arrived at in the 1800s, suggested that there must have been genetic variation among individuals in their ability to communicate with one another. There would have been a series of steps leading from no language at all to language, as we currently know it, with enough evolutionary time and genetic variation separating humans from our non-linguistic ancestors.

More recently, studies of the evolution of the human vocal tract to fit the function of speech have been conducted. Studies of early hominids have shown genetic variation that may have led to the ability to speak. Using fossil evidence and computer modeling, the research concludes that the Cro-Magnon—early modern human beings who lived in Europe between 10,000 and 35,000 years ago—appeared to have an important advantage in their favor: a vocal tract capable of producing all of the sounds of human speech.

Study of the evolution of the human vocal tract led scientists to study the evolution of the human brain. It is likely that the throat and mouth would not have evolved the way they did to facilitate language while compromising eating and breathing if the brain had not been capable of producing and comprehending language.

By 1950 the debate of language as evolution or divine miracle continued. The question of how children acquire language became the inquiry that captivated researchers. The acquisition of language may not appear initially to be very different from the other things that children learn, but it became a pivotal research question because of the on-going developments of evolutionary theory.

Contrary to both theories, B. F. Skinner (1904-1990), an American behavioral psychologist, proposed in 1952 that speech is a learned behavior, one reinforced by the stimulus; response and reinforcement can explain how and why language is learned. By receiving positive reinforcement for sounds, words, and sentences, a child is able to gradually shape his/her verbal skills over time to approximate the language of the community.

Impact

In 1957 the publication of Syntactic Structures by American linguist Noam Chomsky (1928- ) revolutionized the inquiry into language acquisition. He proposed a theory that would account for both linguistic structure and for the creativity of language—the idea that human beings can create entirely original sentences and understand sentences never spoken before.

Chomsky suggested that children are born with the ability to understand the formal principles of grammatical structure, in marked contrast to the idea that language is essentially a system of grammatical habits established by training and experience. Children cannot possibly learn the full rules and structure of languages strictly by imitating what they hear. Instead, nature gives human children a head start by wiring them from birth with the ability to acquire their parent's native language; they can fit what they hear into a pre-existing template for the basic structure shared by all languages.

Current research within the last 10 years supports Chomsky's theory. Linguists have conducted research that suggests that within 48 hours of birth infants show a preference for the language of their parents. Infants can perceive the entire range of phonemes (sounds that make up words), and by the time they are 8 months of age they have begun to distinguish between nouns and verbs. By the age of 16 months most children know where a word belongs in a sentence, and by the age of 3 years most children have the essential patterns of grammar sorted out. All normal children by the age of 4 years, regardless of intelligence, are proficient speakers of their native language.

When Chomsky first voiced his idea that language is hardwired in the brain, he didn't have the benefit of the current findings in cognitive science, which has begun to pry open the human mind with sophisticated research and computer modeling. Until recently, linguists could only marvel at how quickly children master the abstract rules of language that give every human being who can speak (or sign) the power to express an infinite number of ideas from a finite number of words.

Chomsky proposed that children are born with the help of a "language acquisition device," preprogrammed circuits in the brain. Ninety percent of the sentences spoken by a three-year old are grammatically correct. It appears that the baby's brain is humming with activity. Neurobiologists once assumed that the wiring in a baby's brain was set at birth. After that, the brain, like arms and legs, just grew larger. Images made using brain-scanning technique have revealed that when a baby is eight or nine months old, the part of the brain that stores and indexes many kinds of memory becomes totally functional. This is precisely when babies appear to attach meaning to words.

Other leaps in a child's language development coincide with remarkable changes in the brain. For example, an adult listener can recognize eleph as elephant within 400 milliseconds because of an ability called fast mapping, which demands that the brain process speech sounds very quickly. To understand strings of words, humans have to identify individual words rapidly. At 15 months a child needs more than a second to recognize a familiar word, like dog. At 18 months the child can understand the word almost immediately, and by two years of age she knows the word in 600 milliseconds, as soon as the word has been spoken.

This ability coincides with a dramatic reorganization of the child's brain, in which language-related operations, particularly grammar, shift from both sides of the brain into the left hemisphere. While infants and toddlers work with language in both hemispheres of the brain, most adult brains process grammar almost entirely in the left temporal lobe.

Although the ability to acquire language appears to be innate in the child's brain, they need human interaction to attach meaning to words. They need to hear people speaking and conversing for this remarkable ability to emerge. Hearing more than one language in infancy and early childhood makes it easier for a child to hear the distinctions between phemones of another language later on. It also appears that the window of opportunity begins to narrow around age six. Children who do not learn a second language by age 12-15 will have difficulty becoming fluent in another language. This is a compelling argument for teaching a second language in elementary school, when the brain is primed for acquiring language.

Linguists have a long way to go before they can say exactly how a child goes from babbling to talking, what the first languages might have been like, or how the brain transforms thoughts into words, sentences, and complex ideas. However, it appears that innate brain wiring plus experience and practice equal language knowledge and ability. Continued research into human evolution and brain development will perhaps lead towards an answer of how human beings acquire language. In the meantime it is accepted that language is one of the great wonders of the natural world.

LESLIE HUTCHINSON