Lifespan Development. Tara L. Kuther

days. The relevance of context is also illustrated by the infants’ loss of the ability to discriminate the Mandarin contrast several days after training, presumably in the absence of ongoing exposure to the Mandarin language (Fitneva & Matsui, 2015).

      Social interaction is vital to language learning. In the study just described, the English-learning infants did not learn the Mandarin phonetic contrast when they were exposed to it only by audio or video. Live interaction may have increased infants’ motivation to learn by increasing their attention and arousal. Or perhaps live interaction provides specific information that fosters learning, like the speaker’s eye gaze and pointing coupled with interactive contingency (Kuhl et al., 2003).

      In addition, social input, such as the quality of mother–infant interactions, plays a critical role in determining the timing of infants’ narrowing of speech sound discrimination. Specifically, infants who experience high-quality interactions with their mothers, characterized by frequent speech, show a narrowing earlier, as early as 6 months of age (Elsabbagh et al., 2013).

      Prelinguistic Communication

      At birth, crying is the infant’s only means of communication. Infants soon learn to make many more sounds, like gurgles, grunts, and squeals. Between 2 and 3 months of age, infants begin cooing, making deliberate vowel sounds like “ahhhh,” “ohhhh,” and “eeeee.” Infants’ first coos sound like one long vowel. These vocal sounds are a form of vocal play; they are likely to be heard when babies are awake, alert, and contented. At the cooing stage, infants already use pauses that are consistent with the turn-taking pattern of spoken conversations. With age, the quality of coos changes to include different vowel-like sounds and combinations of vowel-like sounds (Owens, 2016). Babbling, repeating strings of consonants and vowels such as “ba-ba-ba” and “ma-ma-ma,” begins to appear at about 6 months of age.

      Babies learn language by hearing others speak and by modifying their babbling in response to caregiver interactions.

      Eric Scouten / Alamy Stock Photo

      At first, babbling is universal. All babies do it, and the sounds they make are similar no matter what language their parents speak or in what part of the world they are raised. However, infants soon become sensitive to the ambient language around them, and it influences their vocalizations (Chen & Kent, 2010). In one study, French adults listened to the babbling of a French 8-month-old and a second 8-month-old from either an Arabic-speaking or a Cantonese-speaking family. Nearly three quarters of the time, the adults correctly indicated which baby in the pair was French (Boysson-Bardies et al., 1984). By the end of the first year, infants’ babbling sounds more like real speech as they begin to vary the pitch of their speech in ways that reflect the inflections of their native languages (Andruski, Casielles, & Nathan, 2013). For example, in spoken English, declarative sentences are characterized by pitch that falls toward the end of the sentence, whereas in questions, the pitch rises at the end of the sentence. Older babies’ babbling mirrors these patterns when they are raised by English-speaking parents, while babies reared with Japanese or French as their native languages show intonation patterns similar to those of the respective languages (Levitt et al., 1992). Longitudinal observations of infants raised in Catalan-speaking environments likewise show that their babbling shifts to mirror intonations in native speech (Esteve-Gilbert et al., 2013).

      Language acquisition, as mentioned, is a socially interactive process: Babies learn by hearing others speak and by noticing the reactions that their vocalizations evoke in caregivers (Hoff, 2015; Kuhl, 2016). Social interaction elicits cooing, and infants modify their babbling in response to caregiver interactions (Tamis-LeMonda, Kuchirko, & Song, 2014). For example, when mothers of 9½-month-old infants speak in response to their infants’ babbling, infants restructure their babbling, changing the phonological pattern of sounds in response to their mothers’ speech (Goldstein & Schwade, 2008). Babbling repertoires reflect infants’ developing morphology and are a foundation for word learning (Ramsdell, Oller, Buder, Ethington, & Chorna, 2012). Language development follows a predictable pattern.

      First Words

      Eleven-month-old William was wide eyed as his father handed him a ball and said, “Ball!” “Ba!” said William. William now understands many words and is beginning to try to utter them. Throughout language development, babies’ receptive language (what they can understand) exceeds their productive language (what they can produce themselves; Tamis-Lemonda & Bornstein, 2015). That is, infants understand more words than they can use. Research suggests that infants may understand some commonly spoken words as early as 6 to 9 months of age, long before they are able to speak (Bergelson & Swingley, 2012; Dehaene-Lambertz & Spelke, 2015).

      At about 1 year of age, the average infant speaks his or her first word. At first, infants use one-word expressions, called holophrases, to express complete thoughts. A first word might be a complete word or a syllable. Usually, the word has more than one meaning, depending on the context in which it is used. For example, “Da” might mean, “I want that,” “There’s Daddy!” or “What’s that?” Caregivers usually hear and understand first words before other adults do. The first words that infants use are those that they hear often or are meaningful for them, such as their own name, the word no, or the word for their caregiver. Infants reared in English-speaking homes tend to use nouns first, as they are most concrete and easily understood (Waxman et al., 2013). For example, the word dog refers to a concrete thing—an animal—and is easier to understand than a verb, such as goes. In contrast, infants reared in homes in which Mandarin Chinese, Korean, or Japanese is spoken tend to learn verbs very early in their development in response to the greater emphasis on verbs in their native languages (Waxman et al., 2013).

      Regardless of what language a child speaks, early words tend to be used in the following ways (MacWhinney, MacWhinney, & Brian, 2015; Owens, 2016):

       Request or state the existence or location of an object or person by naming it (car, dog, outside).

       Request or describe the recurrence of an event or receipt of an object (again, more).

       Describe actions (eat, fall, ride).

       Ask questions (what? that?).

       Attribute a property to an object (hot, big).

       Mark social situations, events, and actions (no, bye).

      Learning Words: Semantic Growth

      “I can’t believe how quickly Matthew picks up new words. It’s time for us to be more careful about what we say around him,” warned Elana. Her husband agreed, “He’s only 2 years old and he has quite a vocabulary. Who would think that he’d learn so many words so quickly?” By 13 months of age, children begin to quickly learn the meaning of new words and understand that words correspond to particular things or events (Woodward, Markman, & Fitzsimmons, 1994). Most infants of Matthew’s age expand their vocabularies rapidly, often to the surprise of their parents. Infants learn new words through fast mapping, a process of quickly acquiring and retaining a word after hearing it applied a few times (Kan & Kohnert, 2008; Marinellie & Kneile, 2012). At 18 months, infants are more likely to learn a new word if both they and the speaker are attending to the new object when the speaker introduces the new word (Baldwin et al., 1996). Two-year-olds have been shown to be able to learn a word even after a single brief exposure under ambiguous conditions (Spiegel & Halberda, 2011) or after overhearing a speaker use the word when talking to someone else (Akhtar, Jipson, & Callanan, 2001). Between 24 and 30 months, infants can learn new words even when their attention is distracted by other objects or events (Moore, Angelopoulos, & Bennett, 1999).

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