28-2 What are the milestones in language development, and how do we acquire language?

Make a quick guess: How many words of your native language did you learn between your first birthday and your high school graduation? Although you use only 150 words for about half of what you say, you probably learned about 60,000 words (Bloom, 2000; McMurray, 2007). That averages (after age 2) to nearly 3500 words each year, or nearly 10 each day! How you did it—how those 3500 words could so far outnumber the roughly 200 words your schoolteachers consciously taught you each year—is one of the great human wonders.

Could you even state your language’s rules of syntax (the correct way to string words together to form sentences)? Most of us cannot. Yet before you were able to add 2 + 2, you were creating your own original and grammatically appropriate sentences. As a preschooler, you comprehended and spoke with a facility that puts to shame college students struggling to learn a foreign language.

We humans have an astonishing facility for language. With remarkable efficiency, we sample tens of thousands of words in our memory, effortlessly assemble them with near-perfect syntax, and spew them out, three words a second (Vigliocco & Hartsuiker, 2002). Seldom do we form sentences in our minds before speaking them. Rather we organize them on the fly as we speak. And while doing all this, we also adapt our utterances to our social and cultural context, following rules for speaking (How far apart should we stand?) and listening (Is it OK to interrupt?). Given how many ways there are to mess up, it’s amazing that we master this social dance. When and how does it happen?

Receptive LanguageChildren’s language development moves from simplicity to complexity. Infants start without language (in fantis means “not speaking”). Yet by 4 months of age, babies can recognize differences in speech sounds (Stager & Werker, 1997). They can also read lips: They prefer to look at a face that matches a sound, so we know they can recognize that ah comes from wide open lips and ee from a mouth with corners pulled back (Kuhl & Meltzoff, 1982). This marks the beginning of the development of babies’ receptive language, their ability to understand what is said to and about them. Infants’ language comprehension greatly outpaces their language production. Even at six months, long before speaking, many infants recognize object names (Bergelson & Swingley, 2012, 2013). At 7 months and beyond, babies grow in their power to do what you and I find difficult when listening to an unfamiliar language: to segment spoken sounds into individual words.

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Productive LanguageLong after the beginnings of receptive language, babies’ productive language, their ability to produce words, matures. They recognize noun–verb differences—as shown by their responses to a misplaced noun or verb—earlier than they utter sentences with nouns and verbs (Bernal et al., 2010).

Before nurture molds babies’ speech, nature enables a wide range of possible sounds in the babbling stage, beginning at around 4 months. Many of these spontaneously uttered sounds are consonant-vowel pairs formed by simply bunching the tongue in the front of the mouth (da-da, na-na, ta-ta) or by opening and closing the lips (ma-ma), both of which babies do naturally for feeding (MacNeilage & Davis, 2000). Babbling does not imitate the adult speech babies hear—it includes sounds from various languages. From this early babbling, a listener could not identify an infant as being, say, French, Korean, or Ethiopian. Deaf infants who observe their deaf parents signing begin to babble more with their hands. (Petitto & Marentette, 1991)

By about 10 months old, infants’ babbling has changed so that a trained ear can identify the household language (de Boysson-Bardies et al., 1989). Without exposure to other languages, babies lose their ability to hear and produce sounds and tones found outside their native language (Meltzoff et al., 2009; Pallier et al., 2001). Thus, by adulthood, those who speak only English cannot discriminate certain sounds in Japanese speech. Nor can Japanese adults with no training in English hear the difference between the English r and l. For a Japanese-speaking adult, la-la-ra-ra may sound like the same syllable repeated. A Japanese-speaking person told that the train station is “just after the next light” may wonder, “The next what? After the street veering right, or farther down, after the light?”

Around their first birthday, most children enter the one-word stage. They have already learned that sounds carry meanings, and if repeatedly trained to associate, say, fish with a picture of a fish, 1-year-olds will look at a fish when a researcher says, “Fish, fish! Look at the fish!” (Schafer, 2005). They now begin to use sounds—usually only one barely recognizable syllable, such as ma or da—to communicate meaning. But family members learn to understand, and gradually the infant’s language conforms more to the family’s language. Across the world, baby’s first words are often nouns that label objects or people (Tardif et al., 2008). At this one-word stage, a single inflected word (“Doggy!”) may equal a sentence (“Look at the dog out there!”).

At about 18 months, children’s word learning explodes from about a word per week to a word per day. By their second birthday, most have entered the two-word stage (TABLE 28.1). They start uttering two-word sentences in telegraphic speech. Like yesterday’s telegrams that charged by the word (TERMS ACCEPTED. SEND MONEY), a 2-year-old’s speech contains mostly nouns and verbs (“Want juice”). Also like telegrams, it follows rules of syntax, arranging words in a sensible order. English-speaking children typically place adjectives before nouns—white house rather than house white. Spanish reverses this order, as in casa blanca.

Moving out of the two-word stage, children quickly begin uttering longer phrases (Fromkin & Rodman, 1983). If they get a late start on learning a particular language, such as after receiving a cochlear implant or being adopted by a family in another country, their language development still proceeds through the same sequence, although usually at a faster pace (Ertmer et al., 2007; Snedeker et al., 2007). By early elementary school, children understand complex sentences and begin to enjoy the humor conveyed by double meanings: “You never starve in the desert because of all the sand-which-is there.”

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The world’s 6000+ or so languages are structurally very diverse (Evans & Levinson, 2009). Linguist Noam Chomsky has argued that all languages nonetheless share some basic elements, which he calls universal grammar. All human languages, for example, have nouns, verbs, and adjectives as grammatical building blocks. Moreover, said Chomsky, we humans are born with a built-in predisposition to learn grammar rules, which helps explain why preschoolers pick up language so readily and use grammar so well. It happens so naturally—as naturally as birds learn to fly—that training hardly helps.

We are not born with a built-in specific language, and languages are much more diverse than the universal grammar idea implies (Bergen, 2014; Ibbotson, 2012). Europeans and Native Australia–New Zealand populations, though geographically separated for 50,000 years, can readily learn each others’ languages (Chater et al., 2009). And whatever language we experience as children, whether spoken or signed, we all readily learn its specific grammar and vocabulary (Bavelier et al., 2003). Yet no matter what language we learn, we start speaking it mostly in nouns (kitty, da-da) rather than in verbs and adjectives (Bornstein et al., 2004). Biology and experience work together.

Statistical LearningWhen adults listen to an unfamiliar language, the syllables all run together. A young Sudanese couple new to North America and unfamiliar with English might, for example, hear United Nations as “Uneye Tednay Shuns.” Their 7-month-old daughter would not have this problem. Human infants display a remarkable ability to learn statistical aspects of human speech (Aslin & Newport, 2012; Werker et al., 2012). Their brains not only discern word breaks, they statistically analyze which syllables, as in “hap-py-ba-by,” most often go together. After just two minutes of exposure to a computer voice speaking an unbroken, monotone string of nonsense syllables (bidakupadotigolabubidaku …), 8-month-old infants were able to recognize (as indicated by their attention) three-syllable sequences that appeared repeatedly (Saffran et al., 1996, 2009).

In further testimony to infants’ surprising knack for soaking up language, research shows that 7-month-olds can learn simple sentence structures. After repeatedly hearing syllable sequences that follow one rule (an ABA pattern, such as ga-ti-ga and li-na-li), infants listened longer to syllables in a different sequence (an ABB pattern, such as wo-fe-fe, rather than wo-fe-wo). Their detecting the difference between the two patterns supports the idea that babies come with a built-in readiness to learn grammatical rules (Marcus et al., 1999).

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Critical PeriodsCould we train adults to perform this same feat of statistical analysis later in the human life span? Many researchers believe not. Childhood seems to represent a critical (or “sensitive”) period for mastering certain aspects of language before the language-learning window closes (Hernandez & Li, 2007). People who learn a second language as adults usually speak it with the accent of their native language, and they also have difficulty mastering the new grammar. In one experiment, Korean and Chinese immigrants considered 276 English sentences (“Yesterday the hunter shoots a deer”) and decided whether they were grammatically correct or incorrect (Johnson & Newport, 1991). All had been in the United States for approximately 10 years: Some had arrived in early childhood, others as adults. As FIGURE 28.1 reveals, those who learned their second language early learned it best. The older one is when moving to a new country, the harder it will be to learn its language and to absorb its culture (Cheung et al., 2011; Hakuta et al., 2003).

The window on language learning closes gradually in early childhood. Later-than-usual exposure to language (at age 2 or 3) unleashes the idle language capacity of a child’s brain, producing a rush of language. But by about age 7, those who have not been exposed to either a spoken or a signed language gradually lose their ability to master any language.

The impact of early experiences is evident in language learning in prelingually (before learning language) deaf¹ children born to hearing-nonsigning parents. These children typically do not experience language during their early years. Natively deaf children who learn sign language after age 9 never learn it as well as those who lose their hearing at age 9 after learning a spoken language such as English. They also never learn English as well as other natively deaf children who learned sign in infancy (Mayberry et al., 2002). Those who learn to sign as teens or adults are like immigrants who learn English after childhood: They can master basic words and learn to order them, but they never become as fluent as native signers in producing and comprehending subtle grammatical differences (Newport, 1990). Moreover, the late learners show less right hemisphere brain activity in regions that are active as native signers read sign language (Newman et al., 2002). As a flower’s growth will be stunted without nourishment, so, too, children will typically become linguistically stunted if isolated from language during the critical period for its acquisition.

More than 90 percent of all deaf children are born to hearing parents. Most of these parents want their children to experience their world of sound and talk. Cochlear implants enable this by converting sounds into electrical signals and stimulating the auditory nerve by means of electrodes threaded into the child’s cochlea. But if an implant is to help children become proficient in oral communication, parents cannot delay the surgery until their child reaches the age of consent. Giving cochlear implants to children is hotly debated. Deaf culture advocates object to giving implants to children who were deaf prelingually. The National Association of the Deaf, for example, argues that deafness is not a disability because native signers are not linguistically disabled. More than five decades ago, Gallaudet University linguist William Stokoe (1960) showed that sign is a complete language with its own grammar, syntax, and meanings.

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Deaf culture advocates sometimes further contend that deafness could as well be considered “vision enhancement” as “hearing impairment.” Close your eyes and immediately you, too, will notice your attention being drawn to your other senses. In one experiment, people who had spent 90 minutes sitting quietly blindfolded became more accurate in their location of sounds (Lewald, 2007). When kissing, lovers minimize distraction and increase sensitivity by closing their eyes.

People who lose one channel of sensation compensate with a slight enhancement of their other sensory abilities (Backman & Dixon, 1992; Levy & Langer, 1992). Blind musicians are more likely than sighted ones to develop perfect pitch (Hamilton, 2000). Blind people are also more accurate than sighted people at locating a sound source with one ear plugged (Gougoux et al., 2005; Lessard et al., 1998). And when reading Braille—requiring sensitive touch perception—the unused processing power of the visual cortex gets used (Amedi et al., 2003).

In deaf cats, brain areas normally used for hearing donate themselves to the visual system (Lomber et al., 2010). So, too, in people who have been deaf from birth: They exhibit enhanced attention to their peripheral vision (Bavelier et al., 2006). Their auditory cortex, starved for sensory input, remains largely intact but becomes responsive to touch and to visual input (Karns et al., 2012). Once repurposed, the auditory cortex becomes less available for hearing—which helps explain why cochlear implants are most effective when given before age 2 (Geers & Nicholas, 2013; Niparko et al., 2010).

Living in a Silent WorldWorldwide, 360 million people live with disabling hearing loss (WHO, 2013). Some are profoundly deaf; others (more men than women) have hearing loss (Agrawal et al., 2008). Some were deaf prelingually; others have known the hearing world. Some sign and identify with the language-based Deaf culture. Others, especially those who lost their hearing after speaking a language, are “oral” and converse with the hearing world by reading lips or reading written notes. Still others move between the two cultures.

The challenges of life without hearing may be greatest for children. Unable to communicate in customary ways, signing playmates may struggle to coordinate their play with speaking playmates. School achievement may also suffer; academic subjects are rooted in spoken languages. Adolescents may feel socially excluded, with a resulting low self-confidence. Children who grow up around other deaf people more often identify with Deaf culture and feel positive self-esteem. If raised in a signing household, whether by deaf or hearing parents, they also express higher self-esteem and feel more accepted (Bat-Chava, 1993, 1994).

Adults whose hearing becomes impaired later in life also face challenges. When older people with hearing loss must expend effort to hear words, they have less remaining cognitive capacity available to remember and comprehend them (Wingfield et al., 2005). In several studies, people with hearing loss, especially those not wearing hearing aids, have reported feeling sadder, being less socially engaged, and more often experiencing others’ irritation (Chisolm et al., 2007; Fellinger et al., 2007; Kashubeck-West & Meyer, 2008; National Council on Aging, 1999). They also may experience a sort of shyness: “It’s almost universal among the deaf to want to cause hearing people as little fuss as possible,” observed Henry Kisor (1990, p. 244), a Chicago newspaper editor and columnist who lost his hearing at age 3. “We can be self-effacing and diffident to the point of invisibility. Sometimes this tendency can be crippling. I must fight it all the time.” Helen Keller, both blind and deaf, noted that “Blindness cuts people off from things. Deafness cuts people off from people.”

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I [DM] understand. My mother, with whom we communicated by writing notes on an erasable “magic pad,” spent her last dozen years in an utterly silent world, largely withdrawn from the stress and strain of trying to interact with people outside a small circle of family and old friends. With my own hearing declining on a trajectory toward hers, I find myself sitting front and center at plays and meetings, seeking quiet corners in restaurants, and asking my wife to make necessary calls to friends whose accents differ from ours. I do benefit from cool technology (see www.hearingloop.org) that, at the press of a button, can transform my hearing aids into in-the-ear loudspeakers for the broadcast of phone, TV, and public address system sound. Yet I still experience frustration when, with or without hearing aids, I can’t hear the joke everyone else is guffawing over; when, after repeated tries, I just can’t catch that exasperated person’s question and can’t fake my way around it; when family members give up and say, “Oh, never mind” after trying three times to tell me something unimportant.

As she aged, my mother came to feel that seeking social interaction was simply not worth the effort. I share newspaper columnist Kisor’s belief that communication is worth the effort (p. 246): “So, … I will grit my teeth and plunge ahead.” To reach out, to connect, to communicate with others, even across a chasm of silence, is to affirm our humanity as social creatures.