How to Read WISC-V Results: FSIQ, Index Scores and Discrepancies

WISC results are easiest to read in four steps: (1) use the Full Scale IQ to get the overall level, (2) compare the index scores to see strengths and weaknesses, (3) check whether a gap is statistically meaningful and also rare, and (4) set everything against the examiner's observations and your child's daily life. Every number is a relative position against a mean of 100 (a mean of 10 for subtests), and it should be read as a range that includes measurement error. This article is for parents who have just received a score report, and it explains what each number means, how to read it, common misconceptions, and how to use the results at school, with sources.

WISC-V and WISC-IV: the indexes on the score report

The current Japanese edition is the WISC-V, for ages 5 years 0 months to 16 years 11 months. It was published in 2021 and went on sale in February 2022; the FSIQ is derived from seven subtests, which take about 45 to 60 minutes to administer (Nihon Bunka Kagakusha). A 21-subtest version that adds the complementary indexes was also released in July 2026. The indexes that appear on the score report are as follows.

• Full Scale IQ (FSIQ): overall intellectual level
• Primary indexes (5): Verbal Comprehension (VCI), Visual Spatial (VSI), Fluid Reasoning (FRI), Working Memory (WMI), Processing Speed (PSI)
• Ancillary indexes (5): Quantitative Reasoning (QRI), Auditory Working Memory (AWMI), Nonverbal (NVI), General Ability (GAI), Cognitive Proficiency (CPI)
• Complementary indexes (21-subtest version): Naming Speed (NSI), Symbol Translation (STI), Storage and Retrieval (SRI)

If your child was tested some time ago, it may have been the WISC-IV (the Japanese edition was published in December 2010) (Matsuda, 2013). The WISC-IV has four indexes: Verbal Comprehension, Perceptual Reasoning (PRI), Working Memory, and Processing Speed. The area covered by Perceptual Reasoning in the WISC-IV is split into two indexes in the WISC-V, Visual Spatial and Fluid Reasoning. Because the number and names of the indexes differ by edition, first check which edition your report is based on.

Reading the numbers: composite scores, scaled scores, confidence intervals, and percentiles

The FSIQ and the index scores (composite scores) are standard scores with a mean of 100 and a standard deviation of 15 (Matsuda, 2013). This is the same scale as ordinary IQ, so you can check the position on the IQ reference table and the IQ distribution data. For example, 115 is one standard deviation above the mean, roughly the top 16% of children the same age; 85 is one standard deviation below, roughly the bottom 16%; and about 68% of all children fall between 85 and 115.

Subtest scaled scores have a mean of 10 and a standard deviation of 3, range from 1 to 19, and 8 to 12 is generally considered average (Pearson). A scaled score of 13 is one standard deviation above the mean, the same position as a composite score of 115. A percentile is a rank among children the same age: the 92nd percentile means the child scored the same as or higher than about 92% of children the same age.

Composite scores can be reported with 90% and 95% confidence intervals (Matsuda, 2013). Actual reports put it like "FSIQ 79 (90% confidence interval 75-85)" (Kobayashi, 2013), meaning the true value lies somewhere within that range. If you think of it as "somewhere around 75 to 85" rather than exactly 79, a difference of one or two points stops being something to celebrate or worry about. Reports also attach descriptive classifications such as "Average" or "Low Average," but the cutoff scores and labels differ by edition, so go by the wording on your own report.

Reading gaps between indexes: a "significant" gap is not the same as a "rare" one

Gaps between indexes are checked in two stages. The first is whether the gap exceeds measurement error (whether it is statistically significant). In the WISC-IV manual's table, the threshold for a significant gap between Verbal Comprehension and Perceptual Reasoning was 10 points at the 15% level and 13.61 points at the 5% level (Dairoku, 2012).

The second is how often that gap occurs among children in general (the base rate). In the same table, 24.4% of children scored 10 or more points higher on Verbal Comprehension than on Perceptual Reasoning and 26.6% scored 10 or more points lower, so about half had a gap of 10 points or more in one direction or the other; even for gaps of 20 points or more, the figures were 8.6% and 10.0%, together about 1 in 5 (Dairoku, 2012). Specialists have proposed treating a gap as "rare" when it occurs in 10 to 15% or less of the standardization sample (Ueno, 2013).

In other words, even a significant gap is often not unusual among children in general, and having a gap is not in itself a sign of anything abnormal. The same source stresses not to conclude that abilities are uneven just because a gap is significant, and the US publisher's technical report also advises against identifying a learning disability from a single analysis (Pearson, Technical Report #1). A developmental disorder is diagnosed by a physician, taking into account developmental history and difficulties at home and school; WISC score gaps alone do not settle it.

How the five indexes relate to everyday situations

An index gap becomes useful for planning support when it is rare and also matches the difficulties seen in daily life. As a rough guide, here are the situations each index tends to be involved in.

• Verbal Comprehension: understanding what words mean, explaining things, and answering questions
• Visual Spatial: making sense of diagrams, maps, and how shapes fit together (how to train spatial reasoning)
• Fluid Reasoning: finding the rule in an unfamiliar problem (what fluid intelligence is)
• Working Memory: working while holding spoken instructions in mind, and mental arithmetic (how to train working memory)
• Processing Speed: copying from the board, and completing simple tasks accurately within a time limit (how to train processing speed)

That said, a low index is not necessarily the direct cause of a difficulty. Subtest scores also shift with nervousness, physical condition, and fluctuations in attention, so it is important to have the examiner interpret the scores together with behavioral observations made during testing: which items the child struggled with, and how.

After you receive the report: the written interpretation, sharing with school, and retesting

The WISC-IV manual states that test results should be communicated together with a written interpretation, that passing on numbers alone is unethical, and that the summary page of the record form must not be copied and given to non-professionals (Dairoku, 2012). If you received only a table of numbers, ask the examiner for a written report with the interpretation and recommendations for support.

When you ask the school for accommodations, that report becomes the basis for discussion. Japan's Ministry of Education (MEXT) states that reasonable accommodations should ideally be provided after the school, the child, and the parents reach agreement, taking the child's developmental stage into account, and that it is important to write their content into the individual educational support plan (MEXT).

For retesting, about two years is the usual guideline to avoid practice effects. In WISC-III data, retesting within a year (27 children) raised each IQ by 7.5 to 10.2 points, while retesting after two years or more (39 children) showed no change (KAKENHI research report). When taken at a medical institution under Japan's national health insurance, the WISC-V falls under the "extremely complex to administer and process" category worth 450 points in the medical fee schedule (Ministry of Health, Labour and Welfare), so with 30% coinsurance the out-of-pocket cost for the test itself is ¥1,350 (consultation fees and other charges are separate). The Tanaka-Binet Intelligence Scale, which can be used from age 2, reports results differently, and there are reports of the same child scoring higher on it than on the WISC, so do not compare the numbers side by side. Children's testing in general is covered in IQ tests for children.

The WISC is an individually administered test for children, and no online test can replace it. If you as a parent want to experience the mean-100, SD-15 scale and how a profile of domain strengths and weaknesses looks using your own result, BrainRank's free IQ test scores 20 questions (about 10 minutes) across four domains, spatial reasoning, pattern recognition, logical reasoning, and classification, using item response theory (IRT), and returns an estimated IQ along with your strengths and weaknesses by domain. Taking the test is free with no registration; viewing the result, including your estimated IQ, is a one-time payment of ¥300 (tax included), with no subscription or auto-renewal (the result can be reopened for 24 hours after it is first shown, and saved as an image or PDF during that window). Results are estimates for entertainment and self-understanding, not a medical or diagnostic test.