Often when a person is being assessed for academic or occupational difficulties, the WAIS-IV will be administered amidst a battery of psychological tests with similarly ambiguous acronyms. The aim of this article is to provide some clarity about the content and purpose of this commonly used assessment. The goal is to demystify part of the psychometric assessment process, which can be overwhelming at times.

Psychologists are often asked to administer the WAIS-IV (Wechsler Adult Intelligence Scale – Fourth Edition). The WAIS-IV is the “gold standard” in cognitive assessment and claims to measure intellectual performance. The importance of conceptualising intelligence as a performance variable is that it does not really matter how much intelligence an individual has, to adapt to the environment. What really matters is how well they use their intelligence. Since intellectual capacity cannot be seen nor concretely verified, it cannot be reliably measured. However, intellectual performance can be measured and thus, should be the focus of testing. Most other major intelligence tests, (e.g. Stanford-Binet; the Peabody Picture Vocabulary Test; Guilford Intelligence Scales), also view intelligence tests as performance measures.

The WAIS-IV measures intellectual performance as a multidimensional construct. The test contains numerous scales (Indices) assessing qualitatively different types of intellectual functioning. Current intelligence tests view intelligence not as specific abilities emanating from a “general” intellectual capacity, but as different types of intelligence, each being of equal importance.

Apart from providing IQ scores, the WAIS-IV integrates current conceptualisations and recent research to provide the most essential information about a testee’s strengths and areas of difficulty. When being revised, there is a lot of input from practitioners and experts in the field. Over time and after several reviews, the WAIS-IV is concluded to represent significant advances in the understanding of cognitive abilities. The WAIS-IV contains 10 core subtests and 5 additional optional subtests. These are summed to four indexes:

  • Verbal Comprehension Index,
  • Perceptual Reasoning Index,
  • Working Memory Index, and
  • Processing Speed Index.

One Full Scale IQ (FSIQ) is also calculated. These scores range from the lowest (40) to the highest (160) points. Subtests are given for additional examination of processing abilities. The age range for the WISC-IV is 16 years to 90 years and 11 months.

WAIS-IV Indices (aka: indexes)

The following are the four main indices of the WAIS-IV and what they measure:

Verbal Comprehension Index (VCI)

This Index assesses the testee’s ability to listen to a question, draw upon learned information from both formal and informal education, reason through an answer and express thoughts aloud. It can tap preferences for verbal information, a difficulty with novel and unexpected situations, or a desire for more time to process information rather than decide “on the spot.”

Perceptual Reasoning Index (PRI)

The PRI assesses the testee’s ability to examine a problem, draw upon visual-motor and visual-spatial skills, organise their thoughts, create solutions and then test them. It can also tap preferences for visual information, comfort with novel and unexpected situations or a preference to learn by doing.

Working Memory Index (WMI)

The WMI assesses the testee’s ability to memorise new information, hold it in short-term memory, concentrate, and manipulate information to produce some results. It is important in higher-order thinking, learning, and achievement. WMI can tap concentration, planning ability, cognitive flexibility, and sequencing skills, but is sensitive to anxiety. It is an important component of learning and achievement, and ability to work effectively with ideas as they are presented in classroom situations.

Processing Speed Index (PSI)

The PSI assesses the testee’s abilities to focus attention and quickly scan, discriminate between, and sequentially order visual information. It requires persistence and planning ability, but can be impacted by motivation, working under a time pressure, and motor coordination. Cultural factors seem to have little impact on PSI. It is related to reading performance and development too. PSI is related to Working Memory in that increased processing speed can decrease the amount of information a testee must “hold” in working memory.

As an analogy, one can think of the thinking brain like the front entrance to a Victorian style home. There is a porch, front door, a foyer and, of course, the rest of the house. Guests (information) knock at the door and “stand on the porch”(i.e., teacher presents concepts). The host (i.e., the brain) lets the “guest” come into the foyer (i.e., brain perceives the information and registers that it is there). The host helps guests take off their coats and boots (i.e., the brain organizes and clarifies the information for storage), and brings them into the house (i.e. encodes the information into longer term memory). If the host takes too long to perform “hosts tasks” and get the guests into the living room, some guests may become impatient and leave (i.e., some information is not encoded).

Finding Assistance

At Strategic Psychology in Canberra, we offer a comprehensive, individually-tailored assessment service that is suitable for children, adolescents and adults who are having difficulties with academic and work functioning. The WAIS-IV is just one of the numerous assessments our clinicians are trained to administer. If you would like to make an appointment for yourself or your child to discuss the possibility and usefulness of administering an assessment, please contact us on (02) 6262 6157 or email support@strategicpsychology.com.au.

Related reading:

How Do I Know if my Child has Learning Difficulties?
Applied Psychometrics 101: What does the WASI-IV Measure?
“None of the Above” What IQ Doesn’t tell you about race by Malcom Gladwell