CHAPTER 33

Speech and Language Development: Normal Patterns and Common Disorders

Geeta Grover, MD, FAAP, and Michelle L. Wahlquist, CCC-SLP

The ability to communicate through language is a uniquely human skill. It develops in a predictable, orderly sequence, beginning in infancy with nonverbal forms and eventually progressing to the use of verbal language. When discussing the development of a child’s communication skills, professionals often use the terms “speech” and “language.” Speech refers to the articulation and production of speech sounds within the mouth, whereas language involves comprehension and expression; language is the understanding and use of words, phrases, and gestures to convey intent. Normal hearing is essential to the development of both speech and language.

Language is often thought of as encompassing 2 components: receptive language and expressive language. Receptive language refers to the ability to understand others, whereas expressive language is the ability to produce communication to convey meaning to others. Although most people think of language simply in terms of only receptive and expressive language, several other critical components of language development must be present for a child to develop effective communication. These include joint attention, play, and social-pragmatic language.

The development of normal speech and language skills is an important developmental milestone that is eagerly awaited by parents. Normal patterns of language development should be as familiar to pediatricians as all other aspects of child development (see Chapter 32), thereby allowing for early identification and referral for suspected delays.

The development of language skills in a normal sequence but at a slower pace than normal is referred to as language delay; language delays may affect only expressive language or both receptive and expressive language (eg, a mixed receptive-expressive language delay). An atypical sequence of language skill acquisition is referred to as a language disorder. Children with developmental language disorders have persistent and significant limitation in their ability to receive or express language.

Epidemiology

The prevalence of specific language impairment in school-age children with no hearing loss or obvious genetic or neurologic condition is approximately 7%. Speech and language disorders are more common in boys than girls and in children with a family history of language, speech, or reading disorders. Good evidence exists that early language impairment is associated with later difficulties learning to read.

Clinical Presentation

Lack of response to sound at any age, difficulty following directions, failure to achieve age-appropriate expressive language skills, reduced eye gaze or gesture, and parental concern about a child’s hearing are the most important signs of hearing or language impairment. Deaf infants coo normally and may even babble; thus, an infant’s vocalizing does not preclude hearing loss.

Pathophysiology

The left hemisphere of the brain is responsible for language skills in 94% of right-handed adults and in approximately 75% of left-handed adults. Peripheral auditory stimuli are transmitted to the primary auditory areas in both temporal lobes. Sounds then undergo a series of analyses, primarily in 3 main areas in the left cerebral cortex: the Wernicke area (ie, auditory association area), which is responsible for language comprehension; the Broca motor speech (ie, motor encoding) area, which is responsible for the preliminary conversion of language into motor activity; and the primary and supplementary motor cortices, which control the movements necessary for speech. This complex process is responsible for the comprehension and production of language.

For children to be successful communicators, they must be competent in all 5 critical domains of language development—joint attention, play, receptive language, expressive language, and social-pragmatic language—which are discussed herein in order of developmental progression by timing of acquisition (Figure 33.1). Additionally, a brief description of speech sound production, which also is important for successful communication, is provided.

The foundation of language development begins with eye contact, social smiling, and the ability to share attention with others, that is, joint attention. Use of eye gaze provides children with their first experiences with shared meaning, which is crucial to language development. Each time children look at their parent, they are provided with language learning opportunities. While looking at their parents, children begin to recognize and understand the meaning of nonverbal communication, including facial expressions and gestures. While watching a parent’s mouth, they observe how speech sounds are formed. In using eye gaze, children begin to build a relationship and attachment to their parents, providing future motivation to want to communicate. Joint attention is a more advanced form of eye gaze that develops by 12 to 15 months of age. It includes sharing attention by alternating eye gaze between an object of interest, a communication partner, and back to the object. It also involves following the attention of another (eg, following the eye gaze or point of another person). Without a strong foundation in joint attention, a child will have challenges in all other language learning.

Figure 33.1. Progression of language development through the 5 domains: joint attention, play, receptive language, expressive language, and social-pragmatic language.

Children’s language skills evolve primarily through parent-child interactions such as singing, reading, and play. It is within play that children learn early vocabulary, language concepts (eg, big, little, fast, slow), problem solving, organization, turn-taking, and sequencing, all of which are required for successful language use.

The ability to understand the communication of others is called receptive language. Early receptive milestones refer to ability to hear and respond to sound (eg, look toward a rattle being shaken), whereas later milestones reflect ability to understand spoken words, follow directions, recall spoken information, and understand questions. In typical language development, receptive language is more advanced than expressive language. Children must understand a concept before they can verbally express that same concept.

The means by which children express their thoughts and ideas through gesture, spoken words, and written communication is called expressive language. Early expressive milestones relate to speech production of vowels and simple consonants (eg, cooing, babbling); later, children begin to express themselves with gesture. Eventually, children use expressive language to convey their intent to others through single words; short phrases; simple sentences, including grammatical structures (eg, past tense [“-ed”]); and eventually in organized storytelling.

Social-pragmatic language refers to the way in which language is understood and used in a social context. It is the “unspoken,” social rules of conversation. Development of social-pragmatic language is a long-term process that begins in infancy with a child’s use of eye gaze, gesture, vocalizations, and single words to communicate with others for a variety of reasons (eg, to request, to comment, to protest, to show off, to share information). Important early milestones presenting between 9 and 12 months of age include protoimperative pointing (to request) and protodeclarative pointing (to show). Social-pragmatic language skills continue to develop and become more refined into late adolescence. Later developing skills include understanding and use of appropriate body language, initiating and maintaining conversation, staying on topic, taking the perspective of others, and using humor. Social-pragmatic language deficits are a core feature of autism spectrum disorder (ASD). Because ASD currently affects 1 in 59 children, all health professionals should be mindful of social-pragmatic language development and deficits (see Chapter 132).

For children to use language to communicate effectively, they must be intelligible to others. Speech sound production, which often is called “articulation,” refers to how a child uses the structures of the mouth to produce speech sounds. Like language, speech sounds follow a developmental progression. Speech disorders include problems in the production of speech sounds. Speech disorders may affect articulation (ie, phonologic disorders), motor planning (ie, childhood apraxia of speech), motor strength (ie, dysarthria), fluency (ie, stuttering), or voice (ie, quality, tone, pitch, volume). By 3 years of age, a child should be at least 75% intelligible to strangers. By 4 years of age, a child should be 100% intelligible, although speech production errors (eg, “wabbit” for rabbit) may persist. This reflects the “rule of 4s,” that is, 50% intelligible by age 2 years, 75% by age 3 years, and 100% by age 4 years.

Early language exposure through caregiver-child interaction is vital for the development of communication, cognitive, and academic skills. Earlier research reported that by the time a child is 4 years of age, a difference in word exposure of up to 30 million words may exist between children living in higher socioeconomic environments compared with those living in lower socioeconomic environments. Newer data support this finding when comparing families from socioeconomic extremes (ie, top and bottom 2% of families), although they suggest that the gap may be closer to 4 million words for families in less extreme poverty. Regardless the size, a gap exists between children living in more privileged environments and those living in more impoverished environments. Research also suggests that expressive language vocabulary at age 3 years is predictive of language and reading achievement up to 9 to 10 years of age (see Chapter 34). Knowledge of normal play as well as social-pragmatic, receptive, and expressive language skills is essential to recognition and identification of developmental delays (Table 33.1). Box 33.1 lists “danger signals” that indicate possible delays and serves as a guide for referral to specialists. The American Academy of Pediatrics reports that by age 18 months children should have an expressive vocabulary of 10 to 25 words and at age 24 months children should be using a vocabulary of at least 50 words. It is important to recognize that a vocabulary of 50 words at 24 months is not an average vocabulary size, with some children producing fewer words and some producing more words. Rather, the use of 50 words at 24 months is a minimum single word vocabulary for a child of that age. Literature in the field of speech-language pathology suggests that, on average, children 24 months of age are able to produce 200 to 300 words, with vocabulary expanding to 1,000 words by age 3 years. Thus, if a health professional sees a 24-month-old child who appears to be “struggling” to reach the 50-word milestone, language development should be monitored closely. The presence of additional language concerns or risk factors for language delay or hearing impairment warrants referral to a pediatric audiologist and pediatric speech pathologist. Children must be able to understand and express at least 50 words before they can begin combining words into 2-word combinations. It is important to remember that by age 3 years, 75% of children’s speech should be intelligible to strangers.

Differential Diagnosis

The various causes of delayed language development include hearing loss, disorders of central nervous system processing, anatomic abnormalities, and environmental deprivation (Box 33.2). Although birth order (eg, the belief that younger children speak later than firstborn children because older siblings speak for them), laziness (eg, “Don’t give him what he wants when he points. Make him ask for it”), and bilingualism are commonly believed to result in speech and language delay, these factors have never been proved to have a contributory role in such delay. For a complete discussion of hearing loss, refer to Chapter 88.

Disorders of central nervous system processing include global developmental delay, intellectual disability, ASD (see Chapter 132), and developmental language problems. Developmental language disorders produce speech or language delays in children in the absence of hearing loss, anatomic abnormalities of the vocal tract, intellectual disability, or global developmental delay. “Late talkers,” that is, children with normal comprehension but who simply begin speaking late, have mild developmental language problems. Children who are completely nonverbal have more severe problems.

Abbreviation: N/A, not applicable.

^a Derived from Westby CE. A scale for assessing development of children’s play. In: Gitlin-Weiner K, Sandgrund A, Schaefer CE, eds. Play Diagnosis and Assessment. 2nd ed. New York, NY: John Wiley & Sons; 2000:15–57.

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