WAIS-IV: Cognitive Assessment for Adults Explained

Overview and Historical Background

The Wechsler Adult Intelligence Scale – Fourth Edition (WAIS-IV; Pearson Assessments, 2012) was designed to evaluate cognitive functioning in adults aged 16 to 90. The WAIS-IV is the most recent updated version (released in 2008) of the most commonly administered intelligence test for adolescents and adults (Canivez, 2010). The test has its roots in the Wechsler–Bellevue Intelligence Scale (Wechsler, 1939). David Wechsler, a psychologist who was dissatisfied with the standard of intelligence testing of his era, based his original tests on his conception of intelligence as "the global capacity of an individual to act purposefully, think rationally, and deal effectively with the environment" (Wechsler, 1939, p. 229). All versions of the WAIS attempt to measure general intelligence and other facets of intelligence through the administration of numerous subtests. Each subtest is an estimate of a particular cognitive ability that serves as an indicator of a specific facet of intelligence (Canivez, 2010).

Major IQ Indices and Subtests

The WAIS-IV has six major IQ indices: a Verbal Comprehension Index (a measure of verbally mediated intelligence), a Perceptual Reasoning Index (a measure of non-verbally mediated intelligence), a Working Memory Index (a measure of the ability to hold and manipulate information in short-term memory), a Processing Speed Index (a measure of how quickly a person can complete automatic tasks), a Full Scale Index (an overall IQ score), and a General Ability Index (an optional index that provides an estimate of general IQ without the contribution of working memory and processing speed; Whiston, 2012). These general indices are calculated from the scores of 10–15 subtests that contribute to the overall score on each particular ability (Canivez, 2010).

Administration Requirements and Standardization

The WAIS-IV requires specific expertise to administer. Pearson Assessments, the manufacturer of the WAIS-IV, restricts purchase of the test to individuals holding doctorate degrees in psychology, education, or related fields with state licensure in their specific discipline (Pearson Assessments, 2012). Specialized training in administering the test is also required by professional organizations such as the American Psychological Association (Pearson Assessments, 2012).

Administration of the basic subtests is lengthy, ranging from 60 to 90 minutes, and the scoring procedures and interpretation are quite complex (Whiston, 2012). Specially trained technicians holding at least a bachelor's degree in a related field may administer the test; however, test interpretation requires an advanced degree in psychology, education, or a related field (Pearson Assessments, 2012; Whiston, 2012). Interpretation includes understanding specific subtest scores and index scores, how they are derived, and behavioral observations made of the client as they work through the assessment. Some subtests require special apparatus (e.g., the Block Design subtest), while others consist solely of question-and-answer exchanges.

Administration is conducted through standardized procedures so that all examinees are tested in nearly the same manner, thereby increasing the reliability and validity of test results (Whiston, 2012). The standardized procedure specifies the types of assistance the administrator may provide and the questions that may be asked or answered to support individual performance. Test items are scored according to instructions in the manual and are then standardized based on normative data collected by the test producer (Canivez, 2010). These standardized scores allow for comparison of individual performance across a wide range of demographic variables. Great efforts are made to ensure that the demographic characteristics of the standardization sample closely mirror those of the population likely to take the test (Canivez, 2010).