April 27, 2021

What do the WISC and WIAT tests actually test?

What do the WISC and WIAT tests actually test?

In my line of work, I often refer parents for an assessment with an Educational Psychologist. This post will explain in detail the WISC and WIAT assessments which are commonly used to assess students and diagnose learning needs.

WISC  - Wechsler Intelligence Scale for Children, 5th Edn. (WISC V)

There are 16 different subtests which are grouped together in different ways to provide these key areas of assessment:

  • Full Scale IQ (FSIQ)
  • Verbal Comprehension (VCI)
  • Visual Spatial (VSI)
  • Fluid Reasoning (FRI)
  • Working Memory (WMI)
  • Processing Speed (PSI)

The 16 Subtests

  • Block design – reproduce a design from coloured blocks
  • Similarities – e.g. how are boys and girls similar?
  • Digit span – repeat back number pattern
  • Picture concepts – pick which pictures go together and why
  • Coding – match code to pictures of numbers
  • Vocabulary – name objects or define a word
  • Letter-Number Sequencing repeat back letters and numbers but change the order
  • Matrix reasoning – 3 pictures shown, which is the missing picture from a choice of pictures
  • Comprehension – e.g. why do we turn out the lights when we leave the room?
  • Symbol Search – search for a symbol in a group
  • Picture completion – identify the missing parts of a picture
  • Cancellation – find a target picture amongst a busy picture
  • Information – general knowledge questions e.g. what do your lungs do?
  • Arithmetic – solve story problems
  • Word reasoning – identify the object from clues given

Full Scale IQ

The FSIQ is derived from seven subtests and summarises ability across a diverse set of cognitive functions. This score is typically considered the most representative indicator of general intellectual functioning. Subtests are drawn from five areas of cognitive ability: verbal comprehension, visual spatial, fluid reasoning, working memory, and processing speed.

Verbal Comprehension Index

The Verbal Comprehension Index (VCI) measures the ability to access and apply acquired word knowledge. Specifically, this score reflects the ability to verbalise meaningful concepts, think about verbal information, and express yourself  using words.

Visual Spatial Index

The Visual Spatial Index (VSI) measures the ability to evaluate visual details and understand visual spatial relationships in order to construct geometric designs from a model. This skill requires visual spatial reasoning, integration and synthesis of part-whole relationships, attentiveness to visual detail, and visual-motor integration.

Fluid Reasoning Index

The Fluid Reasoning Index (FRI) measures the ability to detect the underlying conceptual relationship among visual objects and use reasoning to identify and apply rules. Identification and application of conceptual relationships in the FRI requires inductive and quantitative reasoning, broad visual intelligence, simultaneous processing, and abstract thinking.

Working Memory Index

The Working Memory Index (WMI) measures the ability to register, maintain, and manipulate visual and auditory information in conscious awareness, which requires attention and concentration, as well as visual and auditory discrimination.

Processing Speed Index

The Processing Speed Index (PSI) measures the speed and accuracy of visual identification, decision making, and decision implementation. Performance on the PSI is related to visual scanning, visual discrimination, short-term visual memory, visuomotor coordination, and concentration. The PSI assesses the ability to rapidly identify, register, and implement decisions about visual stimuli.

Wechsler Individual Achievement Test, 3rd Edn. (WIAT III)

The WIAT tests students academic skills in the following areas:

  • Word Reading
  • Reading Comprehension
  • Pseudo-word Decoding
  • Reading Fluency
  • Numerical Operations
  • Maths Problem Solving
  • Maths Fluency
  • Spelling
  • Sentence Composition

Word Reading

  • Individual words
  • Pseudo words
  • Read text – oral reading fluency – measure accuracy and rate

Reading comprehension

  • Read sentence or short text and answer questions about it


  • Solve numerical problems using pencil and paper
  • Maths problem solving subtest requires the student to complete real world problems presented in visual format (graphs, clocks, calendars, pictures etc). Word problems can be read to the student.


  • Write words presented on their own and in a sentence.

Sentence Composition

  • Combine 2 sentences into 1 without changing the meaning
  • Build sentences using a given word.

Testing results

  • The pattern of results will show the students areas of strength and weakness.
  • The pattern of strengths and weaknesses will determine the diagnosis if applicable.

Additional Notes

Ask the psychologist to go through the results with you and explain what they mean for the child. Also, if you need further clarification later, call and ask. There is a lot of information to take in and it is likely to take more than one explanation.

Watch the video


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