Language Disorders in Children

2

Theories and Models of Language Disorders in Children and Adolescents

2.1Typical Language Development

To understand LI, it is helpful to consider the complexity involved in spoken language. Language comprehension and expression involve multiple skills that develop rapidly over the first years of life. For example, comprehension of a full sentence involves parsing complex sound waves into speech sounds and word segments, and applying knowledge of word meanings and grammar (word order and grammatical markers), all in relation to contextual cues and background knowledge that guide interpretation (Bishop, 1997).

Given the complexity of language production and comprehension, children learn language remarkably quickly. Selected milestones of speech/language development and their typical age are shown in Table 9. Milestones give an indication of expected timing of language acquisition; however, there is considerable variability in the age different aspects of language emerge among typically developing children (Fenson et al., 1993).

2.1.1Prenatal and Neonatal Development

Language development begins prenatally, as demonstrated by studies with infants shortly after birth. Newborns can discriminate between auditory stimuli they were exposed to prenatally and comparable, novel stimuli; can distinguish between different languages; show a preference for the language they were exposed to in utero; and prefer their mother’s voice over another woman’s voice, on the first day of life (Decasper & Fifer, 1980; Fava, Hull, & Bortfeld, 2011). Neural studies confirm that language-processing mechanisms, accompanied by brain lateralization, exist at birth. In addition, infants’ sensory capacities support social interaction, which in turn facilitates language development. For example, infants visually orient to human faces more than to comparable stimuli, which supports their attention to linguistic stimulation. These mechanisms and capacities interact with environmental inputs to facilitate language development, as infants tune their general capacity for language learning to their specific language environments (Fava et al., 2011).

Phonological Development

At birth, infants are able to discriminate between almost all speech sounds used in human languages. Over time, infants’ discrimination abilities decrease for sounds that are not included in their language environments. By 6 months of age, infants’ babbling includes the sounds of the primary language(s) of their environment. Some articulation errors are normative in early childhood; by middle childhood, typically developing children have no detectable difficulties with expressive phonology.

Children typically begin to demonstrate phonological awareness between age 2 and 3, when they become aware of rhyming. Around school age, phonological awareness increases as they start to be able to segment words into syllables and speech sounds, and to apply their phonological knowledge to reading and spelling; more sophisticated knowledge develops through to mid to late adolescence (Paul & Norbury, 2012).

Development of Semantics and Grammar

Infants are also primed to learn grammar and semantics, with exposure to sufficient consistent and complex language stimulation. Infants typically begin to understand single words during the first year and to speak their first word around age 1. Semantic development accelerates during the second year to approximately 200–300 words for typically developing children at 24 months (Ganger & Brent, 2004). Young children’s ability to rapidly link new words with their meanings has been termed fast mapping. As this skill improves, supported by phonological and cognitive development, young children are able to learn words more readily, and their vocabulary growth increases (Gershkoff-Stowe & Hahn, 2007).

Children typically begin to combine words into two-word phrases around age 2. Young children acquire structural rules of their language and many word meanings without formal instruction. Acquisition of grammatical rules is acquired through rich exposure to language; adults support grammar learning by recasting (repeating corrected versions) of children’s utterances. A sufficiently large vocabulary is needed to allow young children to absorb rules of grammar based on patterns in the languages they are exposed to in their environments.

Semantics and grammar develop together

Although grammar and semantics are separate domains, they develop in concert. Recent evidence demonstrates that young children use their semantic knowledge to understand grammar (semantic bootstrapping) and their knowledge of grammar to make inferences about word meanings (syntactic bootstrapping). Thus, problems in one domain can affect the other. Genetic influences also appear to affect grammar and semantics jointly (Dionne, Dale, Boivin, & Plomin, 2003).

Grammar development continues through the school age years with increasingly complex syntax, particularly in academic contexts. Most grammatical forms are in place by middle childhood. Complexity and variety of expressive syntax increase through late childhood and adolescence, and a few tenses increase in usage; the full range of adult syntax is generally in place by age 18 (Paul & Norbury, 2012). In contrast, semantic development progresses through adolescence and can continue through the life span as new words and concepts are learned, although the pace of development tends to slow after adolescence (Beitchman et al., 2008).

Pragmatic Development

Pragmatic skills develop through experience of social interaction. Caregivers’ nonverbal and verbal communication introduce social and instrumental functions of language through repeated interactions in different contexts. Infants learn pragmatic skills such as turn taking through play and other interactions with caregivers. Later in their first year, infants begin to use gestures and vocalizations to intentionally communicate.

Pragmatic development continues as children’s linguistic repertoire increases. Children develop pragmatic skills in context, as they experience the consequences of various communication strategies; as well as from direct instruction from caregivers. Pragmatic development overlaps with social development; learning how to use language effectively is a central part of learning how to interact with others. In addition, some aspects of pragmatics rely on cognitive development. For example, the ability to take into account knowledge of the listener and give appropriate context requires theory of mind understanding and perspective-taking abilities. More complex pragmatic skills (e.g., persuasion and exposition) are addressed in educational settings. Pragmatic development can continue into adulthood, as adults may seek to improve their communication skills for particular purposes.

2.1.2Environmental Support for Language Learning

Language is generally acquired without formal instruction, as long as the child is exposed to rich, fully complex language with sufficient language stimulation. However, this statement glosses over the countless social interactions that typically support language development. Infants’ participation in these interactions become increasingly active and intentional; however, the active participation of caregivers continues to be pivotal in supporting language development. For example, the experience of joint attention – the infant and caregiver attending to the same thing, is an important facilitator for language learning as it allows objects or events to be discussed.

Parents and caregivers often engage with young children in a manner that supports language development. For example, conversational recasts (repeating back a corrected version of the child’s utterance), and expansions (repeating back an expanded version of the child’s utterance), which many parents do routinely in their interactions with young children, is a technique used in speech therapy to support development.

The quality and quantity of parents’ interactions with children accounts for considerable variance in children’s language development (Glascoe & Leew, 2010; Hoff, 2006). Cohen (2001) noted that the same parenting skills that foster secure attachment also foster language development: responsiveness and following the child’s lead. Research supports this, showing that child-directed speech that elicits conversation is associated with more rapid language development in comparison with speech to control the child’s behavior. In addition, factors such as quantity of speech directed to young children, variety of words used, and grammatical complexity are associated with rates of language acquisition. Book reading is especially important to language growth because it elicits language from caregivers that is...