Synonyms

VCI; Verbal comprehension scale (WAIS-IV)

Definition

A score derived from administration of selected subtests from the third and fourth edition Wechsler Adult Intelligence Scale (WAIS) and Wechsler Intelligence Scale for Children (WISC) and the fourth edition of the Wechsler Preschool and Primary Scale of Intelligence (WPPSI). The Verbal Comprehension Index (VCI) is designed to provide a measure of verbal acquired knowledge and verbal reasoning.

Current Knowledge

Wechsler Intelligence Scales (WIS)

The WIS family of tests are some of the most widely used test batteries to assess general intellectual ability in adults aged 16 years or older (Wechsler Adult Intelligence Scale; WAIS), children aged 6–16 years (Wechsler Intelligence Scale for Children; WISC), and children aged 2–7 years (Wechsler Preschool and Primary Scale of Intelligence; WPPSI). Since the original development of these tests (WAIS, 1955; WISC, 1949; WPPSI, 1967), all three batteries have been revised on several occasions. The most recent revisions were published in 2012 (WPPSI-IV), 2014 (WISC-V), and 2008 (WAIS-IV).

History

Originally, one of the most prominent features of the WIS was the derivation and interpretation of IQ scores. Using this framework, the Full Scale IQ score provided a measure of general intellectual ability that was differentiated by more specific verbal (Verbal IQ) and visuospatial (Performance IQ) skills. However, the diagnostic utility of IQ scores has been questioned for some time because these scores measure a variety of skills and abilities rather than a pure cognitive construct. For example, early research examining the factor structure of the WAIS and WAIS-R demonstrated that there are at least three cognitive constructs measured by the subtests, rather than the two cognitive constructs originally conceptualized using the Verbal IQ and Performance IQ scores. Although factor-analytic researchers did not agree on the number of meaningful constructs, three factors consistently emerged that were labeled perceptual organization, verbal comprehension, and freedom from distractibility/attention. Regardless of the number of factors, the importance of the multidimensionality of the WIS was quickly recognized which prompted a number of researchers to develop statistical methods that enabled factor-based interpretation of WAIS-R scores not included in the original test manual (e.g., Atkinson 1991).

Evolution

Factor-based interpretation of the WIS was first included in the WISC-III (1991). The addition of a new subtest (i.e., Symbol Search) resulted in the introduction of a four factor scoring system, defined by a Verbal Comprehension Index (VCI), Perceptual Organization Index (POI), Freedom from Distractibility Index (FDI), and Processing Speed Index (PSI). The same four factor scoring system was also included in the WAIS-III (1997) following the inclusion of two new subtests (i.e., Symbol Search and Letter-Number Sequencing), with the exception that the FDI was renamed the Working Memory Index (WMI). For the WISC-III and WAIS-III, the index scores were initially introduced as an “alternative” system for scoring and interpretation that coexisted with the traditional IQ scores which remained unchanged. However, the publication of the WPPSI-IV, WISC-IV, and WAIS-IV represented a significant deferment from the Wechsler scale tradition. The Verbal IQ and Performance IQ scores were excluded for the first time and only the Full Scale IQ score was retained. For the first time in WIS history, the interpretation of the WIS was largely focused on the index scores that were thought to provide a more precise measurement of multiple cognitive abilities assessed by these batteries. For the WISC-IV, the index scores include VCI, WMI, PSI, and the renamed POI – Perceptual Reasoning Index (PRI). For the WISC-V, the index scores include VCI, WMI, PSI, Visual Spatial Index (VSI), and Fluid Reasoning Index (FRI). The PRI/POI was replaced with the VSI and FRI, allowing for more nuanced communication of abilities. For the WAIS-IV, the four index scores (now known as “scales”) include the Verbal Comprehension Scale, Perceptual Reasoning Scale, Working Memory Scale, and Processing Speed Scale. For the WPPSI-IV, the index scores include the VCI, WMI, VSI, and, for children ages 4–7, the PSI and FRI.

Subtest Composition

The core subtests used to derive VCI vary across the WAIS-III/IV, WISC-III/IV/V, and WPPSI-IV. For the WAIS-III/IV, the subtests contributing to the VCI are Vocabulary, Information, and Similarities. For the WISC-III, the same three subtests are used in addition to the comprehension subtest. For the WISC-IV, the Information subtest was not included in the calculation of VCI and includes only the Vocabulary, Similarities, and Comprehension subtests. For the WISC-V, the core subtests of the VCI include only Vocabulary and Similarities. For the WPPSI-IV, Receptive Vocabulary and Information comprise the VCI in children ages 2–3. For children ages 4–7, Information and Similarities comprise the VCI. The core subtests used to derive VCI across the WAIS, WISC, and WPPSI batteries and revisions are presented below. Only the core subtests (not supplementary) are shown (Table 1).

Verbal Comprehension Index, Table 1 Core subtest composition of VCI
Full size table

See Also