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
http://harcourtassessment.com)
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 WAIS® -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
Vocabulary
-
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
Arithmetic
Note: Most of the information from above is compiled from
Harcourt Assessment, Inc.
Please refer
here for FAQs on WISC-IV
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