11.6 Internal and External Supports for Language Development

How is it that children can learn language so early, with so little apparent conscious effort and without deliberate training? There is no doubt that humans enter the world equipped in many ways for language. We are born with (a) anatomical structures in the throat (the larynx and pharynx) that enable us to produce a broader range of sounds than any other mammal can produce (Lieberman, 2007); (b) brain areas specialized for language (including Broca’s and Wernicke’s areas, discussed in Chapter 5); (c) a preference for listening to speech and an ability to distinguish among the basic speech sounds of any language; and (d) mechanisms that cause us to exercise our vocal capacities through a period of cooing and babbling. There is also no doubt that most of us are born into a social world that provides rich opportunities for learning language. We are surrounded by language from birth on, and when we begin to use it, we achieve many rewards through this extraordinarily effective form of communication.

The Idea of Special Inborn Mechanisms for Language Learning

Chomsky’s Concept of an Innate Language-Learning Device

The linguist Noam Chomsky, more than anyone else, was responsible for drawing psychologists’ attention to the topic of language. In his highly influential book Syntactic Structures (1957), Chomsky characterized grammatical rules as fundamental properties of the human mind. In contrast to an earlier view, held by some psychologists, that sentences are generated in chain-like fashion, with one word triggering the next in a sequence, Chomsky emphasized the hierarchical structure of sentences. He argued convincingly that a person must have some meaningful representation of the whole sentence in mind before uttering it and then must apply grammatical rules to that representation in order to fill out the lower levels of the hierarchy (phrases, morphemes, and phonemes) to produce the utterance.

Chomsky (1957, 1965, 1968) conceived of grammatical rules as aspects of the human mind that link spoken sentences ultimately (through one or more intermediary stages) to the mind’s system for representing meanings. Although specific grammatical rules vary from one language to another, they are all, according to Chomsky, based on certain fundamental principles, referred to as universal grammar, that are innate properties of the human mind. These properties account for the universal characteristics of language (discussed earlier) and for other, more subtle language universals (Pinker, 1994). To refer to the entire set of innate mental mechanisms that enable a child to acquire language quickly and efficiently, Chomsky coined the term language-acquisition device, or LAD. The LAD includes the inborn foundations for universal grammar plus the entire set of inborn mechanisms that guide children’s learning of the unique rules of their culture’s language. Support for the concept of an innate LAD comes partly from observations of language-learning deficits in people who have suffered damage to particular brain areas (discussed in Chapter 5) or who have a particular genetic disorder (specific language impairment), characterized primarily by difficulty in articulating words, distinguishing speech sounds from other sounds, and learning grammatical rules (Gopnik, 1999; Vargha-Khadem & Liégeois, 2007).

Children’s Invention of Grammar

Further support for the LAD concept comes from evidence that young children invent grammar when it is lacking in the speech around them. Here are two examples of such evidence.

Children’s Role in Development of Creole Languages New languages occasionally arise when people from many different language cultures simultaneously colonize an area and begin to communicate with one another. These first-generation colonists communicate through a primitive, grammarless collection of words taken from their various native languages—a communication system referred to as a pidgin language. Subsequently, the pidgin develops into a true language, with a full range of grammatical rules, at which point it is called a creole language. Derek Bickerton (1984) studied creole languages from around the world and found that at least some of them were developed into full languages within one generation by the children of the original colonists. Apparently, the children imposed grammatical rules on the pidgin they heard and used those rules consistently in their own speech—powerful evidence, in Bickerton’s view, that children’s minds are innately predisposed to grammar.

Creating a language When deaf children in Nicaragua were brought together for the first time, in a school community, they gradually created a new sign language. The youngest children contributed most to the grammatical structure of the language.

Ann Senghas

Deaf Children’s Invention of a Grammatical Sign Language Bickerton’s evidence of children’s role in creating new languages was necessarily indirect, as he was studying languages that emerged many years ago. More recently, Ann Senghas and her colleagues have documented directly the emergence of a new sign language among deaf children in Nicaragua (Senghas & Coppola, 2001; Senghas et al., 2004). Prior to 1977, deaf Nicaraguans had little opportunity to meet other deaf people. There was no deaf community or common sign language, and the deaf were typically treated as though they were intellectually impaired. In 1977 the first Nicaraguan school for the deaf was founded, so deaf children for the first time came into extended contact with one another. On the basis of outmoded ideas, the school did not at first teach any sign language but, instead, attempted to teach the deaf to speak and lip-read the nation’s vocal language (Spanish), an approach that rarely succeeds. Despite the official policy, the students began to communicate with one another using hand signs.

At first their signing system was a manual pidgin, an unstructured and variable amalgam of the signs and gestures that the individuals had been using at home. But over the course of a few years the signs became increasingly regularized and efficient, and a system of grammar emerged. All this occurred naturally, with no formal teaching, simply through the students’ desires to communicate with one another. Of most significance for our discussion, the new grammar was produced not by the oldest, wisest members of the community but by the youngest. In fact, those who were more than about 10 years old when the deaf community was formed not only failed to contribute to the development of a grammar but learned little of the one that did develop. The sign language invented by the children has since become the official sign language of Nicaragua (Idioma de Señas de Nicaragua). It is a true language, comparable to American Sign Language, in which the morphemes are elementary hand movements and grammatical rules stipulate how the morphemes can be combined and sequenced into larger units.

Children’s improvement of grammar may be viewed by us as a creative act, but it is almost certainly not experienced as that by the children themselves. Children tacitly assume that language has grammar, so they unconsciously read grammar into language even where it doesn’t exist. Just as children learning English overgeneralize grammatical rules when they say things like goed and mouses, and thereby temporarily make English grammar more consistent and elegant than it really is, children exposed to a pidgin language or to an early version of the Nicaraguan sign language may accept the slightest random hint of a grammatical rule as a true rule and begin to use it as such. In the case of a newly emerging language—unlike the case of a long-established language such as English—the children’s rules are incorporated into the language and are learned by the next generation.

Critical Period for Learning the Grammar of One’s First Language

The LAD apparently functions much more effectively during the first 10 years of childhood than later in life. Children who are deprived of the opportunity to hear and interact with a language during their first 10 years have great difficulty learning language later on and never master the grammar of the language they learn. That is one of the lessons learned from observations of deaf children who were not exposed to a true language until adolescence or late in childhood (Mayberry et al., 2002; Senghas et al., 2004). Much more rarely, a hearing person is discovered who was deprived of language throughout childhood, and in every such case that has been documented, the person was subsequently unable to learn language fully (Curtiss, 1989).

The most thoroughly studied language-deprived hearing person is a woman known as Genie. She was rescued in 1970, at age 13, from the inhuman conditions in which her violently abusive father and partly blind and submissive mother had raised her (Curtiss, 1977; Rymer, 1993). From shortly after birth until her rescue, Genie had been locked in a tiny room and exposed to almost no speech. At the time of her rescue, she understood a few words but could not string words together and had learned no grammar. She was then placed in a foster home where she was exposed to English much as infants normally are and received tutorial help. In this environment, she eventually acquired a large vocabulary and learned to produce meaningful, intelligent statements; but even after 7 years of language practice, at age 20, her grammar lagged far behind other indices of her intelligence (Curtiss, 1977). A typical sentence she produced was “I hear music ice cream truck,” and she often misunderstood sentences whose meaning depended on grammar. Over subsequent years of adulthood, her grammar showed little improvement (Rymer, 1993).

Learning within the critical period is much less important for second-language learning than for first-language learning. People who learned their first language within the critical period can learn a second language reasonably well at any time in life, although not quite as well as they could have if they had learned it earlier. Those who learn a second language after the age of about 10 or 11 almost always speak with an accent and generally do not acquire the grammar of the language as fully or easily as do those who learn the language at a younger age (Au et al., 2002; Johnson & Newport, 1989).

The Language-Acquisition Support System

Children come into the world predisposed to acquire language, but they do not acquire it in a social vacuum. Neither Genie nor any other child has ever invented language alone. Normal language development requires not just the LAD but also the LASS—the language-acquisition support system—provided by the social world into which the baby is born (Bruner, 1983).

In Western culture and most others, adults regularly simplify their speech to infants and young children in ways that might help the children learn words and some aspects of grammar. They enunciate more clearly than when speaking to adults, use a more musical tone of voice with greater pitch variation, use short sentences that focus on the here and now, repeat and emphasize salient words, and use gestures to help convey meaning (Snow, 1984; Soderstrom, 2007). A 6-month-old playing with a ball might be told, “Oh, you have a ball. A nice ball. What a pretty ball.” Such speech is often referred to as motherese (although it is not just mothers who speak this way to babies), and more generally as infant-directed speech. Researchers have found that such speech does help infants to distinguish individual words and to make connections between words and their referents (Soderstrom, 2007; Thiessen et al., 2005). Adults also frequently treat infants’ early vocalizations as if they were verbal statements. For instance, a mother or father might respond to the baby’s ba-ba-ga-goo-goo with, “Oh, yes, very interesting!” Such responsiveness can lead to back-and-forth, conversation-like exchanges between infant and adult. It is interesting that mothers of deaf infants also use a form of infant-directed signing, using more repetitions and greater exaggerations of movements to their deaf infants than to their deaf adult friends (Masataka, 1996).

Taking account of the listener Most people automatically simplify their speech when talking to infants and young children. Even young children addressing younger children deliberately slow their rate of speech, choose simple words and grammatical structures, and gesture broadly.

©omborro/Alamy

Parents’ Speech to Infants Affects Language Acquisition

A number of research studies have shown positive correlations between the degree to which mothers speak to their infants, using appropriately simplified language, and the rate at which the infants develop language (Furrow et al., 1979; Tamis-LeMonda et al., 2001). A problem with such studies, however, is that the observed correlations might derive more from genetic similarities between mothers and their children than from differences in the language environments that the mothers provide. Genetically verbal mothers may produce genetically verbal children.

Better evidence for an effect of mothers’ influence on language development comes from a study involving infants who were adopted at birth (Hardy-Brown et al., 1981). In that study, adopted infants’ rates of language development correlated more strongly with their biological mothers’ verbal abilities than with their adoptive mothers’ verbal abilities, but the linguistic environments provided by the adoptive mothers also played a significant role. In particular, infants whose adoptive mothers often responded verbally to their early vocalizations developed language more rapidly than did those whose adoptive mothers were less responsive. Further evidence comes from a series of studies in which parents were trained to engage frequently in back-and-forth verbal play with their infants, from age 3 months to 15 months (Fowler et al., 2006). Those children developed language considerably sooner than did children in otherwise comparable families without such training. Apparently, parents’ verbal responsiveness to infants’ vocalizations plays a significant role in the rate of language acquisition.

Cross-Cultural Differences in the LASS

Cross-cultural research shows that children all over the world acquire language at roughly similar rates, despite wide variations in the degree and manner of adults’ verbal interactions with infants (Ochs & Schieffelin, 1995). For example, the Kalikuli people of the New Guinea rain forest believe that there is no reason to speak to babies who cannot yet speak themselves. These babies hear no motherese, and little speech of any kind is directed toward them. However, unlike infants in our culture, they go everywhere with their mothers and constantly overhear the speech not only of their mothers but of other adults and children around them. This rich exposure to others’ conversations may compensate for the lack of speech directed to them. Apparently, large variations can occur in the LASS without impairing infants’ abilities to learn language.

Bilingualism

Most of our discussion to this point has implicitly assumed that a child is learning just one language—his or her “mother tongue.” However, many people over the globe are bi- or multilingual, speaking two or more languages from early in life. For example, in some European countries, such as Switzerland and Luxembourg, it is typical for people to speak three or four languages, and it is not uncommon for people on the island of New Guinea to be fluent in five or more languages (Diamond, 2013).

There are many factors that influence how easily and how well a child will acquire a second language. Generally speaking, the earlier children are exposed to a second language, the greater the chances that they will become proficient in it. Also, the more similar two languages are to one another (such as English and German versus English and Chinese) the easier it is learn the second language (Snow & Yusun Kang 2006).

Simultaneous and Sequential Bilinguals

The timing of learning a second language makes a difference in proficiency, even when the individual is fully fluent in both languages. Some people are exposed from birth to two languages and are typically equally (or nearly so) fluent in both languages; they are known as simultaneous bilinguals. Other people, called sequential bilinguals, learn a second language after mastering their first. Although sequential bilinguals can gain proficiency in a second language, they rarely attain the level of linguistic mastery as in their first language. They typically retain an accent, for example.

Some neuroimaging research supports the idea that people who master a second language relatively late in life (in adolescence, for example) do so in a different way, neurologically speaking, than people who acquire two languages in childhood (likely simultaneously). For instance, in one study the brains of bilingual adults who learned two languages early in development were contrasted with adults who learned their first language in childhood but their second language in adolescence. For the former group (early bilinguals), the same areas of the brain “light up” when speaking sentences in both languages. This was not the case, however, for the “late bilinguals,” who had learned their second language in adolescence or adulthood. Instead, the pattern of brain activation was different when speaking their first versus their second languages (Wartenburger et al., 2003; see Figure 11.15). This pattern is consistent with the theory that children’s brains are “prepared” early in life for processing language, but, with age, they lose this special ability. It is still possible to learn a second language later in life, but it is not done as easily and is accomplished using different (though overlapping) parts of the brain.

Figure 11.15: Bilingual speakers made grammatical judgments in their second language. For adults who were highly proficient in both languages (A), different parts of the brain were involved in making grammatical judgments for those who learned their second language late (LAHP) versus those who learned their second I anguage early (EAHP).

With permission from Wartenburger, I., Heekern, H. R., Abutalebi, J., Cappa, S. F., Billringer, A., & Perani, D. (2003). Early setting of grammatical processing in the bilingual brain. Neuron, 37, 159–170. Copyright © 2014 Elsevier Inc. All rights reserved.

Costs and Benefits of Bilingualism

Although there are some obvious advantages of speaking two languages, there has also been some considerable debate, especially in education circles, about the costs and benefits of bilingualism (see Bialystok & Craik, 2010). One disadvantage of bilingualism is that children learning two languages at once typically show a delay in syntactic development and have smaller vocabularies in each language and relative to monolingual children. However, bilingual children’s total vocabularies (unique words known in language 1 plus language 2) are comparable to that of monolingual children (Hoff et al., 2012). Other research has shown that bilinguals of all ages are also slower at retrieving individual words from their long-term memories than monolinguals (Bialystok et al., 2008).

On the plus side, in addition to be being able to communicate effectively in two languages, bilinguals are able to recognize a wider range of phonemes than monolinguals (MacWhinney, 2005), and often are more sensitive toward the cultural values of the speakers of both the languages they have mastered (Snow & Yusun Kang, 2006). Relatively recent research has found one perhaps surprising advantage of bilingualism, that of enhanced executive functions (Bialystok, 2001; Bialystok & Craik, 2010). Learning two languages at once is more effortful than learning just one, and bilingual children must work at minimizing interference between their languages. As a result, bilingual children and adults show greater levels of task switching and inhibition than monolinguals (Bialystok & Craik, 2010). There is even evidence that 7-month-old infants growing up in bilingual households show better inhibition and switching abilities (judged by looking time in a study that required infants to look to the right or left to see a dancing puppet, then switching the sides where the puppet was shown) than infants from monolingual homes (Kovács & Mehler, 2009). There is also evidence that bilingualism postpones the decline in executive function in old age (Bialystok et al., 2007).

Language Learning by Nonhuman Apes

To what degree does language depend on special, inborn, language-learning mechanisms that are unique to humans, and to what degree does it depend on more general learning abilities that we share with other animals? That question has motivated much research on the abilities of nonhuman animals to learn human-like languages.

Our closest relatives, chimpanzees and bonobos (discussed in Chapter 3), have brains that are structurally quite similar to ours. Although neither species communicates in its natural environment with anything like the symbol-based, grammar-based system we call human language, both species are highly gregarious and have complex systems of nonverbal communication (Pollick & de Waal, 2007). What would happen if you took such a creature out of its natural community and raised it in a human environment, exposing it to language in the same rich way that human children normally are exposed? Even dogs raised in our homes learn to make some use of our language. My (Peter Gray’s) golden retriever gets excited whenever she hears outside or leash in the conversation around her, and some dogs have learned to respond appropriately to as many as 200 different verbal commands (Kaminski et al., 2004). What might a chimpanzee or bonobo learn if it were raised in a world of humans attempting to communicate with it through language?

In an attempt to find out, Allen and Beatrix Gardner (1978, 1989) began in 1966 to raise a young female chimp named Washoe in the constant presence of people who directed language toward her as well as toward one another. Because the Gardners hoped that Washoe would learn to produce as well as understand language, they and Washoe’s other caretakers used a modified version of American Sign Language rather than a vocal language. Chimpanzees lack the vocal apparatus needed to produce the sounds of human speech, but they have flexible fingers capable of producing manual signs. Washoe’s success in acquiring some of the elements of language inspired many subsequent ape-language projects. Researchers have since studied language learning in a number of other chimpanzees, several bonobos, a gorilla, and an orangutan (Miles, 1983; Patterson & Linden, 1981; Savage-Rumbaugh & Fields, 2000).

The Accomplishments of Kanzi

The most linguistically accomplished ape to date is a bonobo named Kanzi, whose learning has been nurtured and documented for many years by Sue Savage-Rumbaugh and her associates. Before working with Kanzi, Savage-Rumbaugh had been using operant conditioning to teach chimpanzees to communicate through an invented language in which the words are geometric figures, called lexigrams, that are arranged on a keyboard (see Figure 11.16). In 1981, Savage-Rumbaugh was, with little success, training Kanzi’s mother in the lexigram system when she noticed that young Kanzi, who had been allowed to run free in the laboratory, was learning to use some of the lexigrams correctly just by watching, even though he wasn’t being rewarded. This inspired Savage-Rumbaugh to try a different method with Kanzi: immersion in a language culture rather than systematic training.

Figure 11.16: Kanzi using the lexigram keyboard Each symbol on the keyboard is a word. When Kanzi, the bonobo, depresses a key, the symbol is illuminated both on the keyboard and on a larger screen that his caretakers can see. Kanzi also had a portable keyboard that he carried with him as he roamed a forested area with his caretakers. This photo was taken when Kanzi was still quite young, early during his language learning.

Courtesy of Dr. Savage-Rumbaugh, Rumbaugh/Yerkes Language Research Center

Kanzi was continuously free, but not forced, to communicate, using a stationary keyboard in the lab and a portable one outdoors. Kanzi’s caregivers used both spoken English and lexigrams to communicate with him, and they responded to Kanzi’s lexigrams and gestures as parents might to the communicative attempts of their children. Their task was not to teach Kanzi language, but to communicate with him as best they could as they and he went about their daily activities, just as they might with a human child. Our inference from the reports and films on Kanzi is that he received even more linguistic attention and heard even more motherese than does a typical human child.

Kanzi has learned to use roughly 200 lexigrams appropriately, and his behavior indicates that he does not simply use them to get rewards (Lyn, 2007; Savage-Rumbaugh et al., 1986, 1993). For example, he used the lexigram for apple after he already had an apple. He also often announces his intentions before acting. For example, before taking a trip to his tree house, he pressed the lexigram for tree house. In addition, he often combines lexigrams with nonverbal gestures in order to get across more complex ideas than would be possible with the limited set of lexigrams on his board. For example, to get caretaker A to chase caretaker B, he pressed the lexigram for chase and then pushed A’s hand in the direction of B.

Even more impressive than Kanzi’s use of lexigrams is his understanding of spoken English. His behavior suggests that he knows the meanings of at least 500 English words (Savage-Rumbaugh & Fields, 2000). When Kanzi was 8 years old, he was tested for his ability to carry out spoken requests that he had never heard before, such as “Put the egg in the noodles” and “Hammer the ball.” The requests were made by a caretaker who stayed out of view so that nonverbal cues could not guide Kanzi’s behavior. Kanzi carried out most of the requests successfully, performing at a rate comparable to that of a 2.5-year-old human girl who was given the same requests (Savage-Rumbaugh et al., 1993). Kanzi also responded appropriately to requests whose meaning depended on word order, such as “Make the doggie bite the snake” and “Make the snake bite the doggie” (using a toy dog and toy snake as props).

Kanzi is not unique in the ape world. Savage-Rumbaugh and her colleagues have more recently raised another bonobo and a chimpanzee in a manner similar to that of Kanzi, and both animals exhibit language abilities that approach those of Kanzi (Greenfield & Lyn, 2007; Savage-Rumbaugh & Fields, 2000).

Tentative Conclusions from the Ape-Language Studies

Has Kanzi or any other ape learned human language? Some scholars argue about that as if it were a meaningful question, but it isn’t. The answer depends entirely on how one chooses to define human language. A more sensible question is this: What aspects of human language have nonhuman apes been able to acquire, and what aspects, at least so far, seem beyond them? Taking all the studies together, apes appear to be relatively adept at acquiring a vocabulary, and systematic tests suggest that they can use signs and lexigrams as true symbols, standing for referents, and not merely as operant responses to obtain rewards (Lyn, 2007; Sevcik & Savage-Rumbaugh, 1994). Moreover, Kanzi can apparently use word order to decipher the meanings of some simple multiword sentences. However, on the basis of the published research, there is little or no evidence that any ape to date has acquired or invented a rule for distinguishing plural from singular nouns, for marking the tense of verbs, or for marking any words by grammatical class. Apparently, the brain mechanism that makes grammar so easy and natural for human children came about in our evolution sometime after we split off from the line leading to chimpanzees and bonobos.

To us, the most interesting general conclusion from the ape-language research has to do with the conditions that optimize learning. Attempts at deliberate, focused training, involving rewards for correct language usage, have generally failed (for example, Terrace, 1985). In those cases the animals learned to produce word-like gestures as ways to get rewards rather than truly as symbols to label their experiences. Success has occurred when the focus was on communication rather than training. It has occurred when the researchers entered the ape’s world for long periods and brought the ape into their world, using words and sentences along the way (Shanker & King, 2002). This is similar to the conditions in which most human children learn language. The function of language is communication, and a major prerequisite for acquiring language is a desire to communicate.