92 Yoga for Speech-Language Development
that the word “chair” refers to a whole class of chairs (including
lounge chairs, desk chairs, and even high chairs) and to extend
the word “chair” to new, perhaps less familiar, exemplars of the
object (such as beanbag chairs). Child language researchers have
proposed various hypotheses about the nature of the conceptual
basis of children’s early word meanings, which is beyond the
scope of this chapter. However, they generally agree that, in
addition to meaning, children’s mental lexicons contain both
phonological and grammatical information including a word’s
part of speech (Pence Turnbull and Justice 2017). Children with
a variety of neurodevelopmental challenges including language
disorders, intellectual disability, autism spectrum disorder (ASD),
and attention deficit/hyperactivity disorder (AD/HD) can have
problems with the acquisition and use of vocabulary and its
related linguistic concepts. For many of these children, first words
often have a late onset, and new words are acquired more slowly
than in typical development. Lexical acquisition is often targeted
in language intervention for these children.
In discussing children’s mental lexicons, the distinction
between comprehension and production must be considered.
Children’s receptive vocabularies (the words they understand)
often precede and exceed their expressive lexicons (the words
they use). In terms of development, children typically begin
to understand words before they have begun to talk, and they
usually comprehend more words than they say at any point in
development. However, this is not always the case. For example,
some words understood are not necessarily produced, and some
words that children produce are not fully understood. Bloom
and Lahey (1978) suggested that these differences occur because
comprehension and production represent distinct although
interdependent processes in language acquisition. In addition,
children with ASD might say words spontaneously or imitatively
without understanding what they mean. Such imitations are