Chapter 16 Intelligence
Intelligence has been described as the ability to: learn from everyday experience; think rationally; solve problems; act purposively and engage in abstract reasoning. Assumptions about intelligence may affect how we treat others and, for a very small minority of people, their intelligence limits their capacity for self-care.
‘Intelligence’ is a value-laden term. No one wants to be categorized as unintelligent and stereotyping patients or students as ‘intelligent’ or ‘unintelligent’ has consequences for how they are treated. When someone is perceived to be unintelligent people may think it is not worth explaining things to them, resulting in communication breakdown, loss of confidence and uninformed decision-making. This can be especially problematic when we want to encourage self-management and adherence amongst patients (see pp. 94–95). Consequently, health professionals should be cautious about making inferences about their patients’ intelligence.
Intelligence tests are designed to assess how well a person will be able to learn or acquire skills in the future and depend, to some extent, on prior experience and learning. Intelligence tests have been designed to identify individual differences in general reasoning abilities while other aptitude tests, such as tests of musical ability, focus on particular abilities.
Psychologists have distinguished between crystallized and fluid intelligence. Crystallized intelligence is based on skills and knowledge learnt within particular cultures. Fluid intelligence is the capacity to reason and solve problems. Fluid intelligence enables us to learn from experience. Tests that measure abstraction and generalization primarily assess fluid intelligence. For example, the Raven Progressive Matrices test involves a series of pattern-matching problems. Carpenter et al. (1990) examined the reasoning required by this test. They concluded that the test measures the ability to infer abstract relationships and patterns from data and assesses the capacity to decompose problems into subtasks and hold multiple subtasks in mind simultaneously.
Tests that assess vocabulary, general knowledge and scholastic attainment provide information about crystallized intelligence. For example, the Wechsler Adult Intelligence Scale (WAIS) has 11 subscales. Six of these combine to generate a verbal intelligence score: (1) information; (2) comprehension; (3) arithmetic; (4) similarities; (5) digit span; and (6) vocabulary. The other five allow calculation of a performance score: (1) digit symbol; (2) picture completion; (3) block design; (4) picture arrangement; and (5) object assembly. Tests in this measure of intelligence draw on culture-specific learning, assessing crystallized as well as fluid intelligence. For example, ‘What is the capital of Spain?’ (comprehension) and ‘How are a comb and a brush alike?’ (similarities). A children’s version of the test (the Wechsler Intelligence Scale for Children: WISC) is used to assess performance and progress at school.
Intelligence tests are often scored so that the average (or mean) score is 100 and the standard deviation is 15. This means that 68% of the population have scores, or intelligence quotients (IQs), between 85 and 115 and 95% score between 70 and 130. A score of 148 is required to become a member of MENSA, a society that only admits those with an exceptionally high IQ, and people scoring less than 70 (2 standard deviations below the mean) may have learning disabilities and need special help in school and with everyday living.
Scores on intelligence tests tend to be stable. Successive test scores correlate highly and children’s scores, e.g. at age 6, predict adult scores, e.g. at 18 (r = 0.8), although an individual’s score may change over time. Children’s scores also predict performance at school and the number of years they stay at school (r