ABSTRACT
If a child is suspected to have a diffi culty with comprehending language, there are many tools one could use to assess the nature and severity of their impairment. For example, one could administer standardized tests that require children to defi ne words, to match pictures to words or to sentences, to follow a series of instructions, or to listen to sentences or dialogues and answer questions about their content. A suite of well-chosen assessments, in combination with close observation of a child in interaction with others, typically provides a wealth of information. It may reveal,
for example, that the child has low vocabulary knowledge, or a diffi culty interpreting complex sentences, or problems understanding fi gurative language. Such observations provide the clinician with a starting point for intervention and are used by researchers to defi ne, characterize, and categorize the children who participate in their research studies. Beyond surface description and quantifi cation, however, standard assessment instruments are quite blunt tools. They cannot reveal the underlying cause of a child’s comprehension impairment-they cannot determine why a child has low vocabulary knowledge, diffi - culty interpreting complex sentences, or problems understanding complex sentences. Why questions can be addressed at many levels, as refl ected in
the broad range of perspectives brought together in this volume. For example, we can consider the biological bases of language impairment and ask what genetic factors are implicated (Bishop, chapter 5, and Newbury & Monaco, chapter 6, this volume), or ask about its neural basis (Dick, Richardson, & Saccuman, chapter 4, this volume). The aim of this chapter is to highlight the need to think about the nature of language processing, if we are to understand why some people fi nd language comprehension so diffi cult.
