Language Development: An Introduction PDF

1 Language Development An Introduction Learning OutcOmes After completion of this chapter, the reader will be able to: 1. Define the term language. © robert Kneschke/shutterstock 2. Describe how language relates to speech, hearing, and co...

1 Language Development An Introduction Learning OutcOmes After completion of this chapter, the reader will be able to: 1. Define the term language. © robert Kneschke/shutterstock 2. Describe how language relates to speech, hearing, and communication. 3. Describe the major domains of language. 4. identify several remarkable features of language. 5. Discuss the distinction between language differences and language disorders. 1 1 2 www.pearsonhighered.com/pence3e H undreds of scientists worldwide study the remarkable phenomenon of chil- dren’s language acquisition. each year, these scholars publish the results of numerous studies on children’s language development in scientific journals, pursuing answers to such questions as: Does the language a child is learning (e.g., chinese vs. english) influence the rate of language development? How do caregivers’ interactions with their child affect the timing of their child’s first word? Do children who show early delays in language development typically catch up with their peers? Do children learning a signed language develop language similarly to children learning a spoken language? Why do children with autism have such difficulties developing language skills? these questions provide the student of language development a glimpse into many of the interesting topics language scientists focus on in their work around the world. these questions also suggest how important language research is to informing the everyday practices and activities of parents, teachers, psychologists, and other professionals invested in helping children achieve their fullest language development potential. that these questions have yet to be fully answered, shows that the study of language development is a constantly evolving and complex area of science in which practitioners have many more questions than answers. in this chapter, we provide a general introduction to the study of language development and consider five major topics. in the first section, we answer the question “What is language?”, and present a definition of language that we build on throughout this text. in the second section, we discuss differences among speech, hearing, and communication—three aspects of human development and behavior that are closely related but are nonetheless distinct capacities. in the third section, we address the five major domains of language, a topic we introduce here and dis- cuss more fully in chapter 2. in the fourth section, we examine several remarkable features of language, and in the fifth section, we describe differences in and disor- ders of language development—two topics we explore more comprehensively in chapters 9 and 10. WHat is Language? Language Defined You probably have an intuitive sense of what language is because it is a human behavior you have acquired to a sophisticated level and use regularly for various purposes. in fact, you are using your language abilities as you read and analyze the content of this chapter. However, if you take a moment to define language more explicitly, you may find the task challenging. if you were to ask 10 classmates for a definition of language, each would likely respond differently. the same outcome would probably occur if you questioned 10 language researchers. You are also most likely aware that language is a basic and essential human behavior that develops early in life. You probably recognize that language involves words and sentences and both expression (language production) and comprehen- sion (language understanding). in addition, you know language is a process of the brain that helps people communicate their thoughts to other individuals, al- though you may be somewhat unclear about how language differs from speech and communication. However, to be as specific as possible about what language is and is not, let’s look at the official definition of the term language the american speech- Language-Hearing association (1982) uses:  Chapter 1 Language Development 3 The relationship between a word and its referent is arbi- trary. English speakers use the word happy to represent an internal feeling of happi- ness, but any word would do. © Paul Hakimata/Fotolia Language is a “complex and dynamic system of conventional symbols that is used in various modes for thought and communication.” next, we delineate in more detail the specific characteristics of language identified in this definition: 1. Language Is a System of Symbols. the first characteristic of language war- ranting discussion is that it is a code, consisting of a system of symbols called morphemes. morphemes are the smallest units of language that carry meaning; we combine them to create words. some words consist of a single morpheme (e.g., school), but many words comprise two or more morphemes, such as schools (two morphemes—school + -s) and preschools (three morphemes—pre- + school + -s). these symbols can exist in spoken or written format, a point we’ll return to shortly. the term code refers to the translation of one type of information into another type of information; this involves the use of symbols. For humans to develop the capacity to use language thousands of years ago, perhaps the most important pre- requisite was the human ability to use symbols, such as representing a specific concept with a specific sound (christianson & Kirby, 2003). in language, we create words by using morphemes to represent myriad aspects of the world around our language community. For instance, as english speakers, we can represent an inter- nal feeling of happiness by using the single word happy. When we use the word happy in a conversation with other people to describe our feelings, we use the word to translate our feelings. although we can share feelings and ideas through other means—such as gesture, facial expression, and posture—words are much more specific and provide a uniquely powerful tool for communicating. One important characteristic of language code is that the relationship between a word and its referent (the aspect of the world to which the word refers) is arbi- trary. For example, although english speakers recognize that happy refers to a spe- cific feeling, any other word (e.g., sprit, nopic, or grendy) would do. Likewise, one way english speakers can denote plurality is to attach the morpheme -s to words (e.g., pens, dogs). Because the relationship between the plural morpheme -s and its plural marking is arbitrary, english speakers could denote plurality in various other ways. in contrast, the code we use to organize words into sentences is not arbitrary; rather, we must follow specific rules for organizing thoughts into words and sen- tences, as we discuss next. 4 www.pearsonhighered.com/pence3e 2. The System of Language Is Conventional. the second characteristic of lan- guage is that the system of symbols is conventional, so the members of a com- munity or culture can share it. the term conventional means users of a language abide by accepted rules. For instance, speakers of english agree to use the word dog (and related words and synonyms, such as pup, puppy, and canine) to refer to those companionable creatures, rather than other potential words, such as boop or ming. speakers of spanish use a different word to refer to this concept (perro), as do users of american sign Language. adhering to specific conventions allows all members of a language community to use language with one another as a tool for expression. a language community is a group of people who use a common language. in fact, somewhere in the history of the human species, a single language probably emerged within a social community of about 100 hominids (cartwright, 2000). some experts contend that language emerged within this community as a type of grooming behavior, essentially an efficient way to share socially useful in- formation (christiansen & Kirby, 2003). accordingly, the numerous languages of the world emerged from this single community of language users. Language communities emerge for many reasons. some form as a result of geo- graphic circumstances, as in the case of ukrainian, the language people speak in ukraine, a country in the western region of the former soviet union. alternatively, a language community may emerge for sociological reasons, as in the case of He- brew, which many persons of Jewish faith share, or american sign Language, which persons in the u.s. Deaf community use. a language community can organize for economic reasons as well. For instance, the World trade Organization (WtO), a global group that coordinates and regulates trade among 161 countries (as of april, 2015), conducts its activities in english, French, and spanish. 3. The Language System Is Dynamic. the third characteristic of language is that it is dynamic. this means language is in a state of activity and change, both within an individual who is acquiring language and within a community that uses a certain language. Let’s consider first the case of the individual. as we discuss throughout this book, the acquisition of language begins at birth, or even before birth, in utero, and is in a state of change across the lifespan. even as adults, our language skills are dynamic. as one example, we might seek to learn a second language. as another example, as we age, some aspects of our language skill de- cline. We might, for example, have increased difficulty finding the names for things (capuron et al., 2011), which is a normal part of aging. the language a community uses is also very dynamic. When the first edition of this book was published, in 2008, there was no such word as selfie (or selfie stick, for that matter). sometime during the last eight years, this word entered the english language and is now in our vocabulary. in any language, words come and go and other changes happen as well, as we discuss more thoroughly in chapter 9. 4. Language Is a Tool for Human Communication. the final and perhaps most important characteristic of language requiring discussion is that it exists as a tool for communication. Communication is the process of sharing information, such as thoughts, feelings, and ideas, among two or more persons. although other Learn more species are able to communicate, such as dogs, primates, birds, dolphins, and ants, about 1.1 the innate and specialized capacity of humans to use language as a tool to com- as you watch the video municate is what makes the human species unique. For instance, although some titled “What is Language?” primates may communicate alarms to one another using calls, these alarm calls consider the different seem to be general and do not symbolically represent a given predator (e.g., eagle) features of language and (christiansen & Kirby, 2003). experts therefore argue that “language is the most how language differs from distinctive feature that distinguishes humans from other animals” (Wang & minett, other systems of communi- 2005, p. 263). Language itself is what supports the highly complex communication cation. https://www.youtube. enjoyed by the human species, such as your ability to comprehend and learn from com/watch?v=genkKxtk7bw the complex matter contained within this text.  Chapter 1 Language Development 5 Language as a module of Human cognition Beyond its role in supporting human communication, language is a cognitive tool that helps humans to develop the “picture of the world that we use for thinking” (Bickerton, 1995). this “picture of the world” includes not only symbolic repre- sentations of linguistic concepts (e.g., big, fly, crazy) that are organized in a vast network, but also the formal syntactic or grammatical rules that organize these concepts into orderly, surface-level representations. according to this proposition, first and foremost, language is a representational tool people use for thinking, and, second, this tool permits people to communicate their thoughts to other individuals. Language probably emerged in the human species for the latter reason: to pro- vide an efficient and effective means for communication within a community. in other words, language emerged as a cultural and social evolution, rather than a biological evolution: Our need and interest to communicate with others gave rise to the complexity of language over time (christiansen & Kirby, 2003). some experts suggest that language emerged in the human species because of increases in the size of human communities (e.g., from about 50 members in a group to more than 100 members), and therefore increases in the complexity of social dynamics (Dun- bar & aiello, 1993). With time, the neural circuitry of the human brain responded to the adaptive advantage of using language not only as a social tool but also as an inner representational tool, emerging as a specialized part of the human mind (christiansen & Kirby, 2003). the human brain uses language as a representational tool to store informa- tion and to carry out many cognitive processes such as reasoning, hypothesizing, memorizing, planning, and problem solving. these processes are sometimes called higher-level language skills to differentiate them from more basic-level language abilities. When applied to mathematical and scientific tasks, these higher-level abil- ities may be called mathematical reasoning and scientific reasoning; however, it is important to acknowledge the role of language in mathematical and scientific reasoning tasks. For instance, suppose you are asked to complete the following mathematical reasoning task: the average cost of a smart phone in the united states in 2015 is about $250. as- suming the prices of consumer goods decline about 3% per year, how much, on average, would a smart phone cost in 2020? You would have difficultly generating an answer without using language as a tool. although some persons may contend that they think in images and not in words, certain thoughts—such as “my trust in you has been shattered forever by your un- faithfulness”—are impossible to view as images and require language to be invoked as a representational tool (Bickerton, 1995, p. 22). as we consider the definition of language, particularly its relation to cognition, Discussion PoinT we need to explore the concept of modularity. We introduce this concept here, and Too many people in the world are discuss it more thoroughly in chapter 4. Modularity is a cognitive science theory without food. We need a solution about how the human mind is organized within the structures of the brain (Braisby to the global food-shortage prob- lem. Try to reason through a solu- & gellatly, 2012). Questions about modularity concern whether the human brain tion to this problem without using contains a set of highly specific modules—regions of the brain developed to pro- language. is it possible? can an cess specific types of information—or whether the human brain is itself a general- individual engage in complex rea- ized module in which all parts work together to process information. a module is soning without language? a specialized problem-solving device in the brain that responds to information of a restricted type. Because of the specificity of such modules, they are termed domain specific, meaning they can process only very specific types of information, such as depth perception within the visual system. some cognitive theorists contend that the brain consists of very large domain-general modules, which carry out very general tasks like memory and reasoning, as well as domain-specific modules that execute very specific types of tasks. 6 www.pearsonhighered.com/pence3e With respect to language, some language theorists argue that the human brain contains a large number of language-specific modules, tightly clustered and highly interconnected, each of which processes specific types of linguistic information (see curtiss, 2012). such theorists contend that during human evolution, the neural circuitry of the brain became highly specialized in several regions to handle the task of developing and using language (cartwright, 2000). in fact, researchers have long known that specific regions of the brain are associated with specific language abilities. For instance, people who sustain damage to certain areas of the left frontal lobe, such as during a stroke, often exhibit difficulty with basic grammar. these people may omit grammatical markers and speak with a “telegraphic” quality (e.g., “tommy go store now”), which suggests this region of the brain governs aspects of grammar (shapiro & caramazza, 2003). the results of brain-imaging studies of the workings of undamaged brains also indicate that various regions of the brain cor- respond to highly specific aspects of language (Okada et al., 2013), a concept we elaborate on in chapter 3. studies of children with language impairment (a group we discuss more thoroughly in chapter 10) also provide some support for the notion of language modularity. typically developing in all areas except for language, children with a condition called specific language impairment (sLi) exhibit problems in very pre- cise aspects of grammar, such as marking verb tense. Verb tense marking includes, for instance, inflecting verbs with –ed to create the past tense, as in “Juan brushed his teeth.” at ages 4 and 5 years, children with sLi have significant problems with past-tense marking (typically omitting it; clahsen, rothweiler, sterner, & chilla, 2014), even when other aspects of language development are proceeding normally. across any number of languages, including english, german, and swedish, this is a prominent marker of children with sLi (e.g., clahsen et al., 2014). that verb struc- tures are so clearly impaired in children with sLi suggests that, perhaps, there is a particular module of the brain that processes verb structures and that this is the site of disturbance in cases of sLi. the concept of language modularity is not without its critics. some theorists argue that language emerges in response to an individual’s culture rather than in re- sponse to any specific internal architecture. Others argue that language is processed by a general neural network that operates on all aspects of language and that the hypothesized language modules lack “neurological reality” (Bickerton, 1995, p. 76). Bickerton, in a well-reasoned critique of modularity theory as it applies to language, showed that the results of research on disordered language due to developmental disability (e.g., cognitive impairment) and brain injury have failed to support the modularity concept. For instance, Bickerton reviewed studies of persons with dam- age to a specific area of the brain purportedly linked to grammar problems, noting that these individuals showed diverse patterns of syntactic impairment. Because 1.1 the same module was likely damaged in these individuals, the expectation would Check Your be little variability in their impairment. at the same time, it is also important to rec- Understanding ognize that, even if language processes are modular, this does not mean language click here to gauge your functions specific to a given module (or area of the brain) cannot be subsumed by understanding of the another area of the brain when injury occurs. We’ll discuss the notion of brain plas- concepts in this section. ticity in chapter 3. undoubtedly, researchers in the next several decades will better elucidate how language is represented in the neural architecture of the brain. HOW DOes Language reLate tO sPeecH, Hearing, anD cOmmunicatiOn? Language, speech, hearing, and communication together represent basic and inter- related human abilities. although simple forms of communication such as gesturing do not necessarily require language, speech, and hearing, more advanced forms of communication—particularly speaking and listening—require them.  Chapter 1 Language Development 7 Often, the terms language, speech, hearing, and communication are used syn- Discussion PoinT onymously, but in fact they describe substantially different processes. We previously Speech, hearing, communica- defined language as the rule-governed, code-based tool a person uses to represent tion, and language are distinct thoughts and ideas. Once individuals formulate thoughts and ideas, they can com- processes, although people often use the terms interchangeably. municate them to other people using speech or a manual sign system; otherwise, Before reading further, consider individuals can choose to keep thoughts and ideas to themselves (inner language) your definition for each, focusing or can write them down (written language). on what differentiates the four Speech describes the neuromuscular process by which humans turn language processes. into a sound signal and transmit it through the air (or another medium such as a telephone line) to a receiver. Hearing is the sensory system that allows speech to enter into and be processed by the human brain. We described communication pre- viously as the process of sharing information among individuals. communication in the form of a spoken conversation between two persons involves language, hear- ing, and speech; in contrast, communication between two persons in an internet chat room involves only language. speech speech is the voluntary neuromuscular behavior that allows humans to express lan- guage and is essential for spoken communication. in spoken communication, after people formulate ideas in the brain using language, they must then transmit the message by using speech. speech involves the precise activation of muscles in four systems: respiration, phonation, resonation, and articulation. these four systems represent the remarkable coordination of a breath of air as it is inspired into and then expired from the lungs to travel up through the trachea, or windpipe (respi- ration). Within the trachea, the breath of air moves through the vocal cords, which are set into vibration to create one’s voice (phonation). then the breath of air pro- ceeds into the oral and nasal cavities, where it resonates (resonation). Finally, the breath of air is manipulated by the oral articulators—including the tongue, teeth, lips, and jaw (articulation)—to emerge as a series of speech sounds that are com- bined into words, phrases, and sentences. Figure 1.1 illustrates these four systems. When and how humans first began to use speech is the subject of considerable popular, philosophical, and scientific debate; estimates range from 2 million years ago with Homo erectus to only 35,000 years ago with Homo sapiens (cartwright, 2000; Wang & minett, 2005). anatomically modern humans (based on remains Nasal cavity Resonation Oral cavity Teeth Tongue Lips Articulation Jaw (Mandible) Right lung Vocal cords Phonation Trachea Respiration Left lung Figure 1.1 Systems involved with speech production. Adapted from: Justice, Laura m., communication sciences & Disorders: an introduction, 1st ed., ©2006. reprinted and electronically reproduced by permission of Pearson education, inc., new York, nY. 8 www.pearsonhighered.com/pence3e found in ethiopia) existed about 160,000 years ago, and it is believed that speech and language emerged sometime between 160,000 and 50,000 years ago when the human species experienced a “cultural explosion” (Wang & minett, 2005). although this continues to be debated, it is likely that speech became the mode for language expression because of its advantages over other modalities, such as gesturing or grunting (christiansen & Kirby, 2003). Whereas gesturing requires a direct line of sight, speech enables communication in the dark, around corners, and from rela- tively far distances; speech also allows one to communicate when the hands are oc- cupied, as when one is carrying an infant or working manually. in addition, speech allows an individual to communicate with a larger number of persons, which be- came necessary as the group size of early humans increased from small bands of hunter-gatherers of a dozen or so individuals, to larger organized communities of more than 100 members (cartwright, 2000). Finally, and possibly most important, speech provides the medium for sharing language. Model of Speech Production We provide here a relatively basic model of speech production to show how speech moves from the brain to the articulators. a model is a way to represent an unknown event on the basis of the best current evidence governing the event. models of speech production provide a theoretical description of how an individual can move from a cognitive representation (“i forgot to bring paper... i’ll have to borrow a piece … i see she has an extra one in her notebook”) to a clearly articulated spo- ken product (“may i borrow a piece of paper?”). Figure 1.2 presents a basic model of speech production involving three stages. the first stage is a perceptual event: the speech production process is initiated with a mental, abstract representation of the speech stream to be produced. this abstract representation is the language code, which provides a perceptual target of what is to be produced by speech. at the perceptual level, the code is represented by the phoneme. a phoneme is the smallest unit of sound that can signal a difference in meaning; we combine phonemes to produce syllables and words. For instance, the word mama comprises four phonemes, whereas the word my comprises two. in written form, phonemic representations are usually bounded by slashes; thus, the four phonemes in mama are /m/ /a/ /m/ /a/, and the two phonemes in my are /m/ /aI/. conventionally, phonemes are represented by the symbols of the international Perceptual Target Abstract representation of speech sound stream is produced: / // // // / Motor Schema Neurological brain systems produce a rough plan of the abstract representation. General instructions are fed forward in syllable chunks to muscle groups involved with speech: / / / / Speech Output Air pressure is modulated as respiratory flow is sent forward. Articulators and oral cavity are manipulated to produce / /. Feedback Figure 1.2 Model of speech production. Source: Justice, Laura m., communication sciences & Disorders: an introduction, 1st ed., ©2006. reprinted and electronically reproduced by permission of Pearson education, inc., new York, nY.  Chapter 1 Language Development 9 Figure 1.3 international Phonetic Alphabet. Source: international Phonetic association (updated 1993) copyright 1993 by international Phonetic association. Phonetic alphabet (iPa), which is an international set of symbols that represents all of the phonemes of the world’s languages. Figure 1.3 provides a reproduction of the iPa simply for illustrative purposes. (shortly, we’ll focus on the smaller subset of phonemes used in general american english; for a preview, turn to table 1.2.) the second stage of speech production is development of a motor schema to represent the perceptual language–based representation. this is a rough motor plan based on the abstract representation of the perceptual target. the rough plan orga- nizes the phonemes into syllable chunks; for instance, for an infant who wants to call her mother, mama is represented as two syllables to be executed: /ma/ /ma/. the rough plan is sent forward to the major muscle groups involved with speech production. this stimulates the production of speech, or speech output in the 10 www.pearsonhighered.com/pence3e Humans can share language through many means, such as reading, writing, speaking, and communicating manually (e.g., sign language). © golden Pixels LLc/alamy third stage of speech production. the airflow, vocal fold vibration, and oral cavity movements are all finely manipulated to carry out the motor schema and to create speech. Ongoing feedback relays information about speech output back to the origination of the perceptual target and motor schema. Relationship of Speech to Language speech is the voluntary and complex neuromotor behavior humans use to share language. Language does not depend on speech because people can share language by other means, such as writing, reading, and signing, or they can keep it to them- selves as a tool for thinking. However, speech depends wholly on language because language gives speech its meaning. Without language, speech is just a series of meaningless noises. Persons with significant speech disorders, such as those occur- ring in some instances of cerebral palsy (a motor-based disorder present at birth), may be able to produce little or no speech, or they may produce unintelligible speech. these persons cannot use speech to transmit their thoughts to other people. speech and language are largely independent processes; thus, some persons can have no functional speech yet have excellent language skills. as an example, there is one relatively rare condition called locked-in syndrome, in which an individual has completely intact language and cognitive skills, but is unable to perform any volun- tary movements (i.e., has complete paralysis) with the exception of eye movement. Persons with locked-in syndrome can learn to communicate with others through eye movements, such as blinking. However, it is also the unfortunate case that many persons with locked-in syndrome don’t receive the opportunity to communicate because their consciousness is unrecognized by everyone except the person with Discussion PoinT the condition (chisholm & gillett, 2005). nick chisholm, who as a 23-year-old new speech and language are inde- Zealander who was injured while playing rugby, describes his experience after pendent processes, as the case having locked-in syndrome for 5 years this way: “When you’re like this (despite of locked-in syndrome illustrates. can you think of other illustrations having 24 hour care) it’s an incredibly lonely existence at times. it’s amazing how of the independence of speech much time i have to think about things now since the accident. there’s heaps of and language? thoughts that i don’t bother even expressing” (chisholm & gillett, 2005, p. 96). Hearing When people produce speech to share language for communication, not only a sender (the speaker) but also a receiver (the listener) is necessary. the receiver’s task is to receive and comprehend the information the speaker conveys, and hearing  Chapter 1 Language Development 11 is essential to both reception and comprehension of spoken language. Hearing, or audition, is the perception of sound, and it includes both general auditory percep- tion and speech perception. Sound Fundamentals so that you understand hearing and how it relates to language and speech, we will provide a brief overview of acoustics, or the study of sound. the transmission and reception of speech involve four acoustic events: creation of a sound source, vibration of air particles, reception by the ear, and comprehension by the brain (champlin, 2011): 1. Creation of a Sound Source. a sound source sets in motion a series of events. the sound source creates a disturbance—or set of vibrations—in the surround- ing air particles. When you bring your hands together to clap, doing so sets the air particles near the sound source into a complex vibratory pattern. Likewise, when you produce the word coffee, it sets the air particles near the sound source (in this case, just in front of your mouth) into a complex pattern of vibration. 2. Vibration of Air Particles. Fundamentally, sound is the movement or vibration of air particles. the air particles, set in motion by the sound source, move back and forth through the air (or another medium, such as water). How fast the particles move back and forth is the sound frequency, or pitch. How far apart the particles move when they move back and forth creates intensity, or the loudness of the sound. When you clap your hands or say a word, you set the air particles around the sound source into a vibratory pattern, and how the particles move carries information about frequency (pitch) and intensity (loudness). this information is represented in the movements of air particles between the sender and the receiver. 3. Reception by the Ear. the ear is specially designed to channel information car- ried by the air-particle vibrations into the human body. the ear is a complex structure with three chambers. the outer chamber (the outer ear) captures the sound and channels it to the middle chamber (the middle ear). the middle chamber then forwards the acoustic information to the inner chamber (the in- ner ear), which contains the cochlea. From the cochlea, the auditory informa- Learn more tion travels up the auditory nerve to the auditory regions of the brain. about 1.2 4. Comprehension by the Brain. the auditory centers of the brain—located in the left as you watch the video hemisphere—translate the auditory information sent through the ear and along titled “auditory transduc- the auditory nerve. if the information that arrives at the brain involves speech tion (2002),” consider how sounds, the speech and language centers of the brain facilitate the comprehension the physiological process process. if the information that arrives at the brain is not a speech sound (e.g., of hearing can impact a a clap of the hands or the hum of a fan), the speech and language centers are person’s speech and com- not involved. the human brain differentiates sound information as speech and munication skills. https:// nonspeech; in fact, the human ear and the brain are designed to be “remarkably www.youtube.com/ responsive” to processing the sounds of speech (Borden et al., 1994, p. 176). watch?v=Petrigtenoc Speech Perception Speech perception refers to how the brain processes speech and language. speech perception is different from auditory perception, which is a more general term describing how the brain processes any type of auditory information. Processing a clap of the hands or the hum of a fan involves auditory perception, but processing the word coffee requires speech perception. the brain differentiates between gen- eral auditory information and speech sounds, processing speech differently than other auditory stimuli. speech perception involves specialized processors in the brain that have evolved specifically to respond to human speech and language. infants enter the world with biologically endowed processing mechanisms geared to the perception of speech, and with exposure to a specific language (or languages), the perceptual mechanism 12 www.pearsonhighered.com/pence3e is calibrated to reflect this language. calibration of the speech perception mecha- nism is aided by a few capacities of the young child. First, young children show a preference for auditory rather than visual information; this phenomenon is called auditory overshadowing (sloutsky & napolitano, 2003), a principle of early devel- opment suggesting that young children have a bias toward attending to auditory information in their environment. second, young children—mostly infants—show a striking ability to process and analyze speech as a particular type of auditory stim- ulus. From an early age, infants “engage in a detailed analysis of the distributional properties of sounds contained in the language they hear,” which helps calibrate their speech perception abilities for their native language or languages (tsao, Liu, & Kuhl, 2004, p. 1068). in fact, this detailed analysis appears to involve the infant’s use of statistical learning (Hay, Pelucchi, estes, & saffran, 2011). Believe it or not, infants appear to assess statistical regularities among the sounds they hear in the speech stream around them and use these regularities to identify and learn the words of their native language. to learn new words, infants need to be able to isolate words within running speech so as to recognize that the three sounds in cup, blended together, represent the entity “cup.” infants calculate statistics on the durations between phonemes, for instance, to identify whether the phonemes are likely to mark word boundaries, as in my#cup, in which the # marks the word boundary (Hay et al., 2011). at the most basic level, speech perception involves processing phonemic infor- mation, such as the four phonemes in the word coffee (/k/ /a/ /f/ /i/) or the three phonemes in the word cup (/k/ // /p/). sometimes, analogies are made between how the brain processes a series of phonemes in a spoken word, and how a reader reads a series of letters in a written word, as if speech perception involves the se- quential one-on-one processing of individual speech sounds. this analogy is incor- rect. When humans produce phonemes, the phonemes overlap with one another in a process called coarticulation. For instance, the initial /k/ in coffee and the initial /k/ in coop are produced differently because the initial /k/ in each word carries information about the subsequent vowels, which differ. the /k/ in coffee is influ- enced by the subsequent ah sound, whereas the /k/ in coop is influenced by the subsequent oo sound. as a result, the /k/ in coop is produced with rounded lips in anticipation of the oo sound. Coarticulation is the term that describes this “smear- ing,” or overlapping, of phonemes in the production of strings of speech sounds. the articulators (lips, tongue, etc.) coarticulate speech sounds because doing so is much more efficient than producing just one sound at a time, and the speech-pro- cessing mechanisms of the brain have evolved to process the rapidly occurring and coarticulated speech sounds. communication We defined communication previously as the process of sharing information among two or more persons, usually differentiated as the sender (speaker) and the re- ceiver(s) (listeners). typically in communication, only one person is the sender, although this is not always the case, such as when students coauthor a paper. in ad- dition, although communication may at times involve only one receiver, it can also involve numerous receivers, such as when the re-elected president, Barack Obama, gave his second inaugural speech to an estimated audience of more than 1 million on Washington, D.c.’s national mall. regardless of the number of senders and receivers, communication involves four basic processes: formulation, transmission, reception, and comprehension. the sender formulates and then transmits the information he or she would like to con- vey, and the receiver takes in and then comprehends the information. Formulation is the process of pulling together your thoughts or ideas for sharing with another  Chapter 1 Language Development 13 person. Transmission is the process of conveying these ideas to another person, often by speaking, but alternatively by signing, gesturing, or writing. Reception is the process of receiving the information from another person, and comprehension is the process of making sense of the message. Symbolic communication, also called referential communication, occurs when an individual communicates about a specific entity (an object or event), and the relationship between the entity and its referent (e.g., a word) is arbitrary (Leavens, russell, & Hopkins, 2005). For instance, the 1-year-old who says “bottle” to re- quest something to drink is communicating symbolically because the relationship between the word bottle and its referent is arbitrary. symbolic communication also “knows no limitations of space or time” (Bickerton, 1995, p. 15). However, some communication is not symbolic and is thus constrained to Discussion PoinT a particular space and time. Preintentional communication is communication in With iconic communication, the which other people assume the relationship between a communicative behavior relationship between the symbol and its referent. For example, a cat’s purr and an infant’s cry are types of pre- used for communication and the intentional communication. the cat and the baby are communicating, but the referent is transparent. Provide communicative partner must infer the actual referent or goal of the communi- some other examples of iconic cation. the infant’s cry could mean “i am really hungry” or “this blanket is too communication common in the life of a university student. hot.” in contrast, intentional communication is relatively precise in its intent and the relationship between the communicative behavior and its referent is not ar- bitrary. some forms of intentional communication are very transparent (called iconic communication) because of the clear relationship between the message and its referent (Bickerton, 1995). For instance, when an infant points to a bot- tle, or a chimpanzee gestures toward a banana, the act is intentional, iconic communication. Whether communicating intentionally or symbolically, people share informa- tion for three basic purposes: to request (“may i have some cake?”), to reject (“i don’t want this cake”), and to comment (“this cake is delicious”). requesting, re- jecting, and commenting need not use language, as any adult interacting with an 8-month-old infant can attest. infants at this age can request, reject, and comment using an array of nonlinguistic yet intentional means, including crying, laughing, Learn more gesturing, smiling, and cooing. However, as infants develop as language users, about 1.3 they begin to use language and speech as a means to disseminate their needs as you watch the video titled and wants more precisely. By 1 year of age, toddlers use language for all three “Brain Highways: speech purposes, even if their vocabulary is not yet well developed (“Bottle?” “Bottle!” and Language,” consider “Bottle.”). how speech and hearing the combination of speaking and listening is a common mode of commu- processes are related in a nication called oral communication. However, communication need not involve child’s language comprehen- speaking or listening. a person can reject by turning away, a baby can comment sion and how this can im- by smiling, and a dog can request by panting at the door. What is unique about pact a child’s development. human communication though, is the use of language and speech in the commu- https://www.youtube.com/ nication process. in much of this text, we emphasize the development and use of watch?v=1jiFnqKF7ga language as a tool for uniquely human, sophisticated communication. Model of Communication Figure 1.4 provides a model of communication that includes three essential com- ponents: (a) a sender to formulate and transmit a message, (b) a receiver to receive and comprehend the message, and (c) a shared symbolic means for communica- tion. Figure 1.5 shows the roles of language, speech, and hearing in formulation, transmission, reception, and comprehension during communication. in addition to these basic processes is another aspect of communication: feed- back (see Figure 1.4). Feedback is information the receiver provides to the sender. in effective communication, the receiver provides continual feedback, and the sender responds to this feedback to maintain the ongoing effectiveness of the com- munication process. the feedback system is what makes communication active and 14 www.pearsonhighered.com/pence3e Shared means: Sender Receiver Speech Formulation Sign Reception Writing Transmission Comprehension Gesture Feedback Figure 1.4 Model of communication. Source: Justice, Laura m., communication sciences & Disorders: an introduction, 1st ed., ©2006. reprinted and electronically reproduced by permission of Pearson education, inc., new York, nY. FORMULATION Involves Put thoughts and ideas into words to share Language with others. TRANSMISSION Involves Fluently express thoughts and ideas to others. Speech RECEPTION Involves Receive the communication sent by another Hearing person. COMPREHENSION Involves Interpret the communication sent by another Language person. Figure 1.5 roles of language, speech, and hearing in communication. Source: Justice, Laura m., communication sciences & Disorders: an introduction, 1st ed., ©2006. reprinted and electronically reproduced by permission of Pearson education, inc., new York, nY. dynamic. it is active because both sender and receiver must be fully engaged. it is dynamic because the receiver is constantly sending feedback that the sender inter- prets and uses to modulate the flow of communication. a receiver can provide feedback in numerous ways. Linguistic feedback in- cludes speaking, such as saying “i totally agree,” “i hear what you are saying,” or “Wait; i don’t get it.” it also includes vocalizing, such as saying “mm-hmm” or “uh-oh.” Nonlinguistic feedback, or extralinguistic feedback, refers to the use of eye contact, facial expression, posture, and proximity. this type of feedback may supplement linguistic feedback or it may stand alone. Paralinguistic feedback refers to the use of pitch, loudness, and pausing, all of which are superimposed over the linguistic feedback. these linguistic and nonlinguistic forms of feedback keep the communication flowing, and provide the speaker with valuable information con- cerning the receiver’s comprehension.  Chapter 1 Language Development 15 When communicating, peo- ple often supplement their speech and language with nonlinguistic, or extralinguis- tic feedback, such as eye contact, facial expressions, posture, and proximity. © tyler Olson/shutterstock For communication to be effective, the receiver’s feedback is just as important as the information the sender provides. the sender and the receiver use feedback to prevent communication breakdowns from occurring: Child: i need that one. Father: this one? Child: no, that one. Father: this here? Child: no. (starts crying) Father: maybe it’s this one? Child: Yeah, i said that one. if you look closely at this snippet of conversation, you should be able to find a communication breakdown that seems to occur because of inadequacies of both the sender and the receiver. the child appears not to have the language abilities to produce sufficiently explicit information about what he or she desires, and the fa- ther does not provide adequate feedback to clarify the lack of specificity. eventually the father repairs the breakdown, which is called a conversational repair. minor communication breakdowns occur in every conversation but are easily recognized and repaired if the sender is closely monitoring the receiver’s feedback and the receiver is providing ongoing feedback. more serious communication breakdowns occur when receivers do not provide appropriate types or amounts of feedback or when senders do not attend to the feedback. Purpose of Communication the primary purpose of communication is to provide and solicit information. Hu- 1.2 mans communicate to provide information about their feelings and to obtain in- Check Your formation from other people. individuals communicate to share information about Understanding trivial and exciting events and to describe their needs and desires. table 1.1 pro- click here to gauge your vides one system of differentiating the major purposes of communication. all of understanding of the these purposes are vitally important for developing and maintaining social relation- concepts in this section. ships with other people, as well as for meeting personal basic needs and satisfying desires. 16 www.pearsonhighered.com/pence3e TAbLe 1.1 Seven purposes of communication PURPoSe DeSCRiPtioN exaMPLe Instrumental used to ask for something “Will you pass me the butter, please?” Regulatory used to give directions and to direct others “Go ahead and sit down over there.” Interactional used to interact and converse with others “How was the game last night?” in a social way Personal used to express a state of mind or feelings “There is no way i passed that test!” about something Heuristic used to find out information and to inquire “Do you know how much this book is?” Imaginative used to tell stories and to role-play “okay, let’s practice what you’re going to say when you call her.” Informative used to provide an organized description “so, we got to the hotel, and they had no of an event or object record of our reservation. Then, they tell me they have no rooms left at all....” Source: Based on Learning How to Mean: Explorations in the Development of Language Development by m. a. Halliday, 1975, London: arnold; and “Presentation of communication evaluation information” by c. simon and c. L. Holway, in Communication Skills and Classroom Success (pp. 151–199), edited by c. simon, 1991, eau claire, Wi: thinking Publications. WHat are tHe maJOr DOmains OF Language? Form, content, and use Language is a single dimension of human behavior that consists of several distinct domains. in chapter 2 we discuss these domains more deeply; however, we intro- duce them here as their understanding will be useful in chapter 4, when we discuss prominent theories of language development. a classic representation of the domains comprising language distinguishes among content, form, and use (Lahey, 1988). consider the following utterances by 3-year-old adelaide: “i beating you up the stairs.” “i wonned!” “i am so fast.” these utterances provide an array of analytical possibilities for characterizing adelaide’s language. First, you can consider the form of adelaide’s utterances. Form is how words, sentences, and sounds are organized and arranged to convey content. When you consider form, you examine such things as sentence structure, clause and phrase usage, parts of speech, verb and noun structures, word prefixes and suffixes, and the organization of sounds into words. For instance, in examining the form of adelaide’s utterances, note that she uses three simple sentences, the first of which contains a prepositional Discussion PoinT phrase (up the stairs). she uses various parts of speech, including nouns (stairs), in the example of Adelaide’s language, she said the word pronouns (I), articles (the), prepositions (up), verbs (running), and adverbs (so). ade- wonned. What are some possible laide also uses a number of speech sounds, including a variety of vocalic sounds (i.e., explanations for this error? vowels) and several consonantal sounds (i.e., consonants; e.g., /b/, /w/, /f/). in considering form, you must take a closer look at how sentences are structured. examination of adelaide’s sentence structures reveals that each sentence contains a subject, which, in all cases, is the personal pronoun I. each sentence also contains a predicate, or verb, structure. in her three short utterances, adelaide uses three different verb structures. in the first sentence, I beating you up the stairs, she uses the transitive verb beating, which requires an object (i.e., you). note that although she has inflected the verb beat with the present progressive marker -ing to show that the actions are oc- curring continuously in the present, she has also omitted the auxiliary verb am. in the  Chapter 1 Language Development 17 second sentence, adelaide uses the verb wonned. in this case, she has produced the irregular past tense form of win but has added the past tense marker for regular verbs, -ed. this verb is an intransitive verb, which does not require an object, and none is pro- vided. in the third sentence, the verb structure comprises a be verb (am) that serves as the main verb in the sentence and requires a subject complement (so fast). second, you can consider content, which refers to the meaning of language—the words used and the meaning behind them. We humans convey content through our vocabulary system, or lexicon, as we select and organize words to express our ideas or to understand what other individuals are saying. You can consider the content of adelaide’s utterances in a variety of ways: she uses 12 words; of these, she repeats one word (I) several times, for a total of 10 different words. the words beating, wonned, and fast create lexical ties across the utterances because conceptually they work to- gether to denote that a race of some type is occurring. the words she uses and the concepts she expresses through these words are fairly concrete. she does not use fig- urative or idiomatic words, nor does she use abstract language. the focus is clearly on the here and now. Language that focuses on the immediate context is contextualized, and typically the content of highly contextualized language is concrete and supported by cues within the environment (e.g., gestures, facial expressions). thus, in this par- ticular example, the context in which adelaide speaks provides important information that supplements the content of the language. in contrast, imagine that adelaide was telling the story of this race over the telephone to her grandmother. she would need to be much more precise to convey the content. When we share language with little reliance on the context for conveying content, it is decontextualized. third, you can consider the language use. Use pertains to how people draw on language functionally to meet personal and social needs. When you examine this do- main of language, you are asking about the intentions behind the utterances and how well the utterances achieve these intentions. thus, you examine individual utterances to consider their intent. One possible scheme is Halliday’s seven communication func- tions (see table 1.1). For the analysis of adelaide’s language use, you can conclude that the intentions behind her utterances are primarily interactional (language used to interact socially) and personal (language used to express a state of mind). examination of use also involves consideration of how well language achieves Learn more these intentions—for example, whether an individual can maintain a topic through about 1.4 several turns in a conversation, can regulate the participation of other people (e.g., as you watch the video ti- through eye contact, facial expressions, pausing), and can adjust language given tled “Language Domains,” the particular demands of the communicative situation and the listener’s needs. consider how each domain Because analysis of use requires understanding the context in which language is allows for detailed spec- occurring, it may be difficult to evaluate one’s language use by reading a transcript. ificity in communication. For example, you would have no way to know from the transcript of adelaide’s ut- https://www.youtube.com/ terances whether she is meeting the contextual needs of the situation, and whether watch?v=Wrni7VrumJu she is regulating her language use effectively to achieve her intentions. components of Form, content, and use Form, content, and use represent a three-domain system used to represent and orga- nize the major dimensions of language. a five-component system is also often used, which provides a slightly more refined description of the components of each of the three domains. the five components are phonology, morphology, syntax, seman- tics, and pragmatics. the first three—phonology, morphology, and syntax—are three components of form, whereas the components of semantics and pragmatics are syn- onymous with the domains of content and use, respectively. Following is a brief de- scription of each component; these topics are considered in more depth in chapter 2: 1. Phonology (form) refers to the rules of language governing the sounds that make syllables and words. every language has a relatively small number of meaningful sounds, or phonemes.General american english (gae; also called Standard American 18 www.pearsonhighered.com/pence3e TAbLe 1.2 Vowels and consonants of general American english CoNSoNaNt SYMboL exaMPLe CoNSoNaNt SYMboL exaMPLe b bat r or ɹˍ rose p pat s sun d dip ʃ shine t tip f fit g give ʧ church h hot θ think j yes ð that k cat v vet l lot w wash m mine z zag n nose ʒ treasure ŋ ring ʤ jail VoweL SYMboL exaMPLe aRtiCULatoRY FeatUReS i feet high, front, unrounded ɪ fit high, front, unrounded e make mid, front, unrounded ɛ bet mid, front, unrounded æ cat low, front, unrounded u blue high, back, rounded ʊ pull high, back, rounded ɔ bought mid, back, rounded o go mid, back, rounded a box low, back, unrounded ʌ bug mid, central, unrounded ə around mid, central, unrounded ɝ bird mid, central, unrounded ɘ˞ father mid, central, unrounded Source: Justice, Laura m., communication sciences & Disorders: an introduction, 1st ed., ©2006. reprinted and electronically reproduced by permission of Pearson education, inc., new York, nY.  Chapter 1 Language Development 19 English) has about 39 phonemes (give or take a few, depending on the dialect), as shown in table 1.2. gae relies on the combination of 15 vowels and 24 consonants to create about 100,000 words. some languages use more phonemes; others use fewer. allophones are the subtle variations of phonemes that occur as a result of contex- tual influences on how phonemes are produced in different words. For instance, the two /p/ phonemes in pop are produced differently, given the position of each in the word. the initial /p/ is aspirated, meaning that it is produced with a small puff of air. in contrast, the final /p/ is unaspirated. (the final /p/ can be aspirated but typically is not.) the two /p/ sounds in pop are allophonic variations of a single phoneme, and many phonemes have several allophones. in addition, each language has rules governing how sounds are organized in words, called phonotactics. For instance, in english the phoneme /g/ never directly follows /s/ or /l/ at the beginning of a syllable. 2. Morphology (form) pertains to the rules of language governing the inter- nal organization of words. Previously, we defined morpheme as the smallest unit of language that carries meaning; many words contain two or more morphemes. We can “morph” (manipulate) words in a variety of ways to change their meaning. For instance, we can add prefixes to words to change their meaning—such as by adding the morpheme pre- to words to create preschool, predisposition, preview, and pretest. also, we can use suffixes to add grammatical information to words (i.e., to indicate basic grammatical information such as tense or plurality). these types of suffixes are called grammatical morphemes. grammatical morphemes include the plural -s (cat–cats), the possessive ’s (mom–mom’s), the past tense -ed (walk–walked), and the present progressive -ing (do–doing), to name a few. morphology is an important linguistic tool that not only allows us to add precision to language (e.g., “tamika walk” vs. “tamika had walked”), but also to expand vocabulary exponentially using a relatively small core of words (base vocabulary) and morphing them into a much larger pool of word families (e.g., school, schools, schooling, schooled, preschool). 3. Syntax (form) refers to the rules of language governing the internal organi- zation of sentences. Knowledge of the rules governing syntax enables us to readily turn the simple statement He did it into the question Did he do it?, and to embed one simple sentence (e.g., Andre is angry) in another (e.g., Andre is not coming) to produce a complex sentence (e.g., Andre, who is angry, is not coming). syntax is what permits a child to produce a seemingly endless sentence by linking a series of simple sentences: This is Thomas and he is so mad at Lady and Lady goes off the siding and here comes Percy and Thomas gets out of the way and Percy is coming so fast. in short, whereas semantics provides the meaning to utterances, syntax provides the structure. noam chomsky’s well-known proposition that Colorless green ideas sleep furiously illustrates the difference between semantics and syntax, in which a sentence is devoid of meaning but conforms to sophisticated syntactic rules. 4. Semantics (content) refers to the rules of language governing the meaning of individual words and word combinations. When people produce a given word Learn more (e.g., cat) or phrase (black cat), they express a certain meaning. semantics thus about 1.5 involves consideration of the meaning of various words and phrases. For instance, as you watch the video titled you know that a culprit is someone who has done something wrong; the word run “Fantastic Feature We Don’t has many meanings, whereas the word stapler has only one meaning; the phrase Have in the english Lan- bent over backwards has both a figurative and a literal meaning; and the words pa- guage,” consider how english paya, banana, and kiwi go together conceptually. if you ask a person to produce creates form, content, and use the first word that comes to mind when he or she hears the word “vehicle,” the and how other languages do semantic relationship among words might provoke the person to respond “car” (or, the same but with different alternatively, “truck” or “tractor”). Knowledge of semantics tells you something is features. https://www.youtube. wrong with the sentence linguist, noam chomsky produced, Colorless green ideas com/watch?v=QYlVJlmjLec sleep furiously, and differentiates the meaning the words express (semantics) from the grammar that organizes them into a sentence (syntax) (Pinker, 1994). 5. Pragmatics (use) pertains to the rules governing language use for social purposes, and is a synonym for the term social communication. Pragmatics com- 20 www.pearsonhighered.com/pence3e prises the set of rules that govern three important aspects of the social use of 1.3 language: (a) using language for different functions or intentions (communication Check Your intentions); (b) organizing language for discourse, including conversation; and (c) Understanding knowing what to say and when and how to say it (social conventions). in using click here to gauge your language for social purposes, pragmatic rules govern linguistic, extralinguistic, and understanding of the paralinguistic aspects of communication, such as word choice, turn taking, posture, concepts in this section. gestures, facial expression, eye contact, proximity, pitch, loudness, and pauses. WHat are sOme remarKaBLe Features OF Language? Language is one of the most extraordinary capacities of the human species, and young children’s extremely rapid language acquisition is one of the most remark- able aspects of early development. given the thousands of scientific studies explor- ing the extraordinariness of language, including how children go about learning the languages of their communities, you might assume nothing is left to learn about language development. such an assumption could not be further from the truth. there are many mysteries that remain regarding how children develop their lan- guage abilities and, indeed, how humans acquired language in the first place. Why is language such a mystery? in part, its mysteriousness relates to several re- markable features of language that work together to make it a particularly complicated area of study, albeit one that continues to capture the attention of numerous scholars around the world. in this section, we consider five of these remarkable features of lan- guage: acquisition rate, universality, species specificity, semanticity, and productivity. acquisition rate Faced with the task of explaining how children develop their remarkable language skills, scholars have often noted that the sheer acquisition rate of language makes it difficult to study. For instance, consider the following interaction between a mother and her 30-month-old daughter: tajika: thomas the very useful engine is in the siding. Mother: He’s in the what? tajika: the siding. this is the siding. Mother: Oh, that’s the siding? this brief interaction shows the extraordinary capacity of young children to learn and use new words at a stunning rate. Siding is a part of a train track that runs off the main course. in this vignette, tajika has placed her miniature thomas the tank engine on the siding. Her mother did not know the meaning of siding, but tajika clearly did. erica Hoff, a scientist who studies early language development, stated that lan- guage development reveals the genius in all children (Hoff, 2013), whereas others have referred to infants and young children as “scientists in cribs” (gopnik, melt- zoff, & Kuhl, 2009). the reference to children as geniuses and young scientists is based on the fact that children acquire the complexities of language at a seemingly miraculous rate: although at birth children understand and use no words, within a year, they begin to understand and use several words, and by about 24 months, they have a vocabulary of several hundred words and can combine them into short sentences. Whereas the 1-year-old can say only “mama” to request something to drink, the 3-year-old can say, “mom, Daddy said i could have some chocolate milk and i think i’ll have it in the pink sippy cup.” the years of early language acquisition, from birth to about puberty, are often called a critical period (or sometimes a sensitive period) for language development,  Chapter 1 Language Development 21 meaning that a window of opportunity exists during which language develops most rapidly and with the greatest ease. (We will discuss the concept of a critical period in more depth in chapter 3.) a critical period for language development also im- plies periods of time in which the environment has particularly important impacts on language growth. One important study of the critical period, as it applies to language develop- ment, involved research on institutionalization of infants in romania (nelson et al., 2007). institutionalized care in romania, at least until the early 2000s, typically fea- tured very limited stimulation of infants, in part due to the very high child-to-care- giver ratio in such settings (smyke et al., 2007). in this study, institutionalized infants were randomly assigned to remain in institutionalized care or to be placed in foster homes, in which presumably, stimulation would be greater because of a decrease in the child-to-caregiver ratio. an important part of this study, in addition to assess- ing the benefits of foster-care placements, was testing the critical-age hypothesis; the researchers did this by varying the time when children were moved into foster care: 14 children were placed in foster care before 18 months, 16 children between 18 and 24 months, 22 between 24 and 30 months, and 9 after 30 months (nelson et al., 2007). if a critical period is operating, within which language development is most readily influenced by features of the environment, we might expect that chil- dren placed earlier in foster care would exhibit better language skills than children placed later. in fact, this is exactly what researchers found when they measured the language abilities of the foster-care children at 3.5 years of age. On standardized measures of language ability, those placed earlier had the highest scores, and those placed later had the lowest scores, with a gap of about 15 points separating those with the earliest versus the latest placements. the critical period in the human species for language development is similar to the critical periods in other species for acquisition of behaviors considered es- sential for survival. For instance, songbirds show a critical period for song learn- Discussion PoinT ing, although considerable differences in the ways in which songbirds acquire in this section, we consider the songs occur among the more than 4,000 songbird species (e.g., some songbirds concept of critical period as it require early exposure to songs for song learning, whereas others can develop applies to language development. To what other areas of develop- song in isolation; Brenowitz & Beecher, 2005). Because only one species of Homo ment does the concept of critical sapiens exists, the critical period of language development applies to all children period apply? everywhere. universality Language is ubiquitous among the communities of the world. every human cul- ture has one language, and sometimes many languages, and all are equally com-