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Language and nonverbal/visual-motor problem solving are components of the neurocognitive stream of development. Because the most common causes of neurodevelopmental disability affect the brain diffusely (eg, genetic disorders), delays in language development are most commonly accompanied by delays in nonverbal/visual-motor problem-solving development and vice versa. Thus, the most prevalent mild neurodevelopmental difficulty that results in school failure is “slower learning,” where both language and nonverbal/visual-motor problem solving are delayed, resulting in intelligence quotients in the borderline (IQ = 70–79) to low average (IQ = 80–89) range. The globally delayed pattern of slower learning occurs in 22.8% of the population, while the dissociated pattern of learning disabilities occurs in only approximately 5% to 10% of the population. In the dissociated pattern of learning disabilities, there is a discrepancy between cognitive abilities and academic achievement, typically with discrepant or dissociated delays in language relative to nonverbal/visual-motor problem-solving development (as observed in language-based learning disabilities) or discrepant or dissociated delays in nonverbal/visual-motor problem solving relative to language development (as observed in nonverbal learning disabilities). It is also important to note that inadequate academic instruction is a common cause of learning problems. This chapter will review the spectrum of dissociated delays in language and nonverbal/visual-motor problem-solving development, including specific language-based and nonverbal learning disabilities.
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DEFINITIONS OF SPEECH AND LANGUAGE
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Language is defined as a method of both spoken and written communication. Language is made up of multiple components: phonology, morphology, syntax, semantics, and pragmatics. Phonology involves speech sounds (phonemes) that make up words, and morphology involves the units of language (morphemes) that make up words. Syntax is defined as the rules regarding how words can be combined into sentences, including verb tense, word order, and sentence structure. Semantics is defined as the meaning of words in context or when combined into sentences. Pragmatics is defined as the rules for social communication. Language is separated into expressive and receptive components. Expressive language refers to what a child is able to communicate verbally or through the use of signs or gestures. Receptive language refers to what a child is able to understand.
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Speech includes the following components: articulation, fluency, and voice. Articulation involves the production of speech sounds and affects the intelligibility of speech. Fluency refers to the flow of sounds, syllables, and words together to form sentences. Voice includes the anatomical function of the vocal folds as well as airflow to produce sounds.
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SPEECH AND LANGUAGE DEVELOPMENT
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Speech and language development can be divided into 3 periods during early childhood (birth to 2 years of age). The first is the prespeech period, which begins at birth. In the first few months of life, an infant will typically progress from alerting to sound to responding to and seeking familiar voices. An infant’s cry will start to differentiate based on his or her needs. Cooing (the production of vowel ...