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The Wechsler Intelligence Scale for Children - Fourth Edition (WISC–IV)

By Inderbir Kaur Sandhu, Ph.D

Q: How do we know the WISC-IV is a reliable measure of intelligence? What each WISC-IV component measures and how they are indicators for success in school. For example, coding - What does this measure and what does it do to help students in school?

A: Standardized intelligence tests have to adhere to strict guidelines to ensure reliability. Reliability refers to the consistency of a measure. A test is considered reliable if we are able to get the same/similar result repeatedly. For example, if a test is designed to measure intelligence, two of the same form of test (say, Part A and Part B) should bear very close results when administered to a subject. Having said that, it is almost impossible to calculate reliability accurately, but there several different ways to estimate reliability (there are a lot of internet resources on this subject). In this case, the WISC-IV is believed to be a reliable measure of intelligence.

Among other, testing is done when one has some concerns about a child's learning needs and wants to determine the child's learning potential and placement in certain programs (usually gifted programs). Apart from providing IQ scores, the WISC-IV also provides essential information and critical clinical insights into a child's cognitive functioning. It also integrates current conceptualizations and recent research to provide the most essential information about a child's strengths and weaknesses. There is a lot of input from practitioners and experts in the field. Over time and reviews, the WISC-IV (which is an update of the WISC-III) indicates significant advances in the understanding of cognitive abilities.

Administered between 65 and 80 minutes, the WISC-IV contains 10 core subtests and 5 additional subtests. These are summed to four indexes (the Verbal Comprehension Index, the Perceptual Reasoning Index, the Working Memory Index and the Processing Speed Index) and one Full Scale IQ (FSIQ) which ranges from lowest 40 to highest 160 points. Subtests are given for additional examination of processing abilities. The age range for this test is between 6 years and 16 years 11 months. In terms of difference in scores, an individual who has taken the WISC-III, then retested with the WISC-IV may show a 5 point drop in FSIQ. This is due to new aspects of the test, and the novelty of some of the new items and subtests.

The following shows the four main indexes of the WISC-IV and what they measure

Verbal Comprehension Index (VCI)

Measure: Verbal concept formation.

It assesses children's ability to listen to a question, draw upon learned information from both formal and informal education, reason through an answer, and express their 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."
Note: This index is a good predictor of readiness for school and achievement orientation, but can be influenced by background, education, and cultural opportunities.

Perceptual Reasoning Index (PRI)

Measure: Non-verbal and fluid reasoning.

It assesses children's ability to examine a problem, draw upon visual-motor and visual-spatial skills, organize 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)

Measure: Working memory.

It assesses children's ability to memorize new information, hold it in short-term memory, concentrate, and manipulate that information to produce some result or reasoning processes. It is important in higher-order thinking, learning, and achievement. It can tap concentration, planning ability, cognitive flexibility, and sequencing skill, but is sensitive to anxiety too. It is an important component of learning and achievement, and ability to self-monitor.

Processing Speed Index (PSI)

Measure: Processing speed.

It assesses children's abilities to focus attention and quickly scan, discriminate between, and sequentially order visual information. It requires persistence and planning ability, but is sensitive to motivation, difficulty working under a time pressure, and motor coordination too. Cultural factors seem to have little impact on it. It is related to reading performance and development too. It is related to Working Memory in that increased processing speed can decrease the load placed on working memory, while decreased processing speed can impair the effectiveness of working memory.

Based on new neurological models of cognitive functioning, there have a number of improvements in the WISC-IV, namely:

  • Betterment in assessing fluid reasoning

  • Less reliance on speed for PRI - better differentiates PRI from PSI

  • Better assessment of WM through changes made to one test and addition of a new subtest

  • Improved subtest reliabilities, floors and ceilings from WISC-III

  • Enhanced clinical validity, improved reliabilities and validities (updating of norms)

  • Updated art

  • Less cultural, SES or regional bias

  • The integrated version that allows some multiple choice testing of children to see what they know but can not express

Areas of Assessment (from

Subtest Changes
Three WISC-III subtests have been eliminated from WISC-IV: Object Assembly, Mazes and Picture Arrangement. WISC-III subtests that are now supplemental include Picture Completion, Arithmetic, and Information.

New Subtests
Several new subtests are added to reflect current clinical knowledge and practice:

  • Word Reasoning - measures reasoning with verbal material; child identifies underlying concept given successive clues.

  • Matrix Reasoning - measures fluid reasoning a (highly reliable subtest on WAISŪ -III and WPPSI-III); child is presented with a partially filled grid and asked to select the item that properly completes the matrix.

  • Picture Concepts - measures fluid reasoning, perceptual organization, and categorization (requires categorical reasoning without a verbal response); from each of two or three rows of objects, child selects objects that go together based on an underlying concept.

  • Letter-Number Sequencing - measures working memory (adapted from WAIS-III); child is presented a mixed series of numbers and letters and repeats them numbers first (in numerical order), then letters (in alphabetical order).

  • Cancellation - measures processing speed using random and structured animal target forms (foils are common non-animal objects).

In addition, new optional recall procedures have been added to the Coding subtest, including free recall, cued digit recall, and cued symbol recall; a coding copy procedure is also included to allow examination of graphomotor abilities apart from paired-associate learning.

Improvements to Retained Subtests

  • Vocabulary

  • Block Design

  • Arithmetic

  • Improved Materials


  • Picture naming items in the Stimulus Book provide a lower floor

  • Vocabulary words are now displayed in Stimulus Book, in addition to being read aloud

Block Design

  • Reduced time bonus

  • Timed and un-timed norms are now provided


  • Reduced requirement for math knowledge on the Arithmetic subtest

  • No time bonus

  • No text items

  • Picture counting retained for subtest floor

Note: Most of the information from above is compiled from Harcourt Assessment, Inc.

Please refer here for FAQs on WISC-IV

Featured Resource


Essentials of WISC-IV Assessment
Dawn P. Flanagan Ph.D, Alan S. Kaufman Ph.D

The WISC-IV is the top intelligence assessment instrument for children in the US, providing essential information into a child's cognitive functioning. This book applies a new, expanded theory-based approach to interpreting the latest edition of the WISCŪ and provides beginning and seasoned clinicians with comprehensive step-by-step guidelines to administering, scoring, and interpreting this latest revision of the Wechsler Intelligence Scale for Children.

This book provides students and practitioners with an unparalleled resource for learning and application, including expert assessment of the test's relative strengths and weaknesses, valuable advice on its clinical applications, and illuminating case reports.

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