WAIS-IV Wechsler Adult Intelligence Scale - Fourth

WAIS-IV Wechsler Adult Intelligence Scale - Fourth Edition (WAIS-IV) 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 the times, based his original tests on his notion 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 via the administration of numerous subtests. Each of these subtests is an estimate of a particular cognitive ability that is an indicator of a particular facet of intelligence (Canivez, 2010).

The WAIS-IV has six major IQ indices that include a Verbal Comprehension Index (a measure of verbally-mediated intelligence), Perceptual Reasoning Index (a measure of non- -- verbally -- mediated intelligence), a Processing Speed Index (a measure of how quickly a person can complete automatic tasks), a Full Scale Index (and 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 the particular ability (Canivez, 2010). The tests require specific expertise to administer. For instance Pearson Assessments, the manufacturer of the WAIS-IV, will only allow individuals with doctorate degrees in psychology, education or related fields with state licensure in their specific field to purchase the test (Pearson Assessments, 2012). Specialized training in administering the test is required by organizations such as the American Psychological Association, etc. (Pearson Assessments, 2012).

The administration of the basic subtests is lengthy (from 60 -- 90 minutes) and the scoring procedures and interpretation are quite complex (Whiston, 2012). Specially trained technicians can administer the test (these technicians must have at least a bachelors degree in a related field); however, tests interpretation requires an advanced degree in a field such as psychology, education, or related field (Pearson Assessments, 2012; Whiston, 2012).

This interpretation includes understanding the specific subtest scores, Index scores, and how they are derived as well as noting observations of the client as they work their way through the tests during the assessment. Some of the subtests require special apparatus to complete (e.g., Block Design test), whereas others are simply question-and-answer. The administration of the test is completed through standardized procedure such that everyone who receives the test is tested in nearly the exact same manner, thus increasing the reliability and validity of the test results (Whiston, 2012).

The standardized procedure includes defining the types of assistance the administrator can provide and the types of questions that can be answered or asked by the administrator to enhance the performance of individual. The test items are scored via instructions in the manual that the administrator must use during every administration and are then standardized based on normative data that has been collected by the test producer (Canivez, 2010). The standardized scores allow for the comparison of individual efforts across a large domain of demographic variables.

The test manual has information regarding the standardization sample and great efforts are made to make sure that the demographic features of the standardization sample closely mimic the demographic features of the people taking the test (Canivez, 2010). There is strong evidence for reliability of the WAIS-IV based on three types of reliability estimates provided in the manual. Internal consistency estimates across the 13 age groups in a national standardization sample range from .97 for the full scale IQ score and from .87-.98 for the other indices (Canivez, 2010).

Test -- retest reliability with retest periods ranging from eight to eighty two days indicated stable coefficients for the Full Scale IQ and Verbal Comprehension index, whereas several of the Perceptual Processing Index subtest scores had higher practice effects (start). Interrater reliability ranges from .91 -- .97 for the various subtests and indices (Canivez, 2010). Validity estimates for the WAIS-IV are reported based on the factor structure of the tests, test content, convergent and divergent measures of validity, and differences in groups based on the standardization sample.

The correlation matrices indicate that the subtests have significant correlations of subtests in the same domain and are not correlated significantly with other subtests (Canivez, 2010). Confirmatory factor analyses have supported the latent structure of the indices; however, there is some concern that confirmatory factor analytic studies are more supportive of latent factors than exploratory factor analytic studies (Frazier & Youngstrom, 2007) and some critics suggest that more exploratory analyses should be used. In studies of divergent and convergent validity the WAIS-IV has demonstrated adequate performance (Canivez, 2010).

In general, one of the major strengths of the WAIS-IV is its standardization sample that consists of 2200 participants from a wide range of demographic factors based on population census data (Canivez, 2010). Another advantage of the test is the standardized administration procedures that increases the reliability and adds to the potential validity of the instrument. In addition, the core and supplemental subtests supply adequate dimensions and contribute to the magnitude of the abilities that the test assesses which provide a more rounded view of the client's cognitive abilities than previous versions.

The constructs measured.