ABSTRACT
This chapter concentrates upon the neuropsychological value of a cognitive area often termed ‘intelligence’ or ‘intellectual functioning’. The definition usually includes reference to the measurement of IQ and its subtests, and may be used to encompass a much wider range of functions, including concept formation. The discussion which has continued over the years as to the definition and nature of ‘intelligence’, whether IQ tests measure it adequately, and the relative contribution of genetic and environmental factors in its determination are not central, happily, to neuropsychological usage. Tests of intelligence or IQ are used by clinical neuropsychologists as one (albeit central) component in assessing cognitive functioning. The important aspects for neuropsychologists tend to relate to information provided by tests on specific intellectual functions, rather than to overall intelligence level. As there is not a predictable relationship between overall IQ and amount of acquired brain damage, these tests are used to examine patterns of functional impairment and the relationship of these to type of pathology and extent (general, lateralized, localized) of brain lesion. As will be described below, there are particular relationships between test performance and brain lesions which help us to understand what organizational damage the brain has sustained, what its current functional capacities are, and what its future recovery and performance might be. The brain-behaviour relationships which are examined using tests of intellectual functioning need to take account of potentially confounding factors. For example, mood disturbance can often complicate the interpretation of tests of intellectual functioning (see Caine, 1986, for review). Specific comments on the effects of anxiety, depression and other factors upon intellectual performance will be offered in the next section.
