5 Plan A: Standardized measures of IQ and development

Considerations for test selection

When there is a query of intellectual disability, a standardized measure of IQ, along with a standardized measure of adaptive functioning are essential assessment tools. When deciding which test of cognitive/developmental functioning to administer, there are a number of factors to consider. In addition to the things you usually look for in a test, there other factors you should consider in children with motor, sensory, and communication differences.

Test characteristics: For children whose developmental level is likely to be highly discrepant from their chronological age, it is helpful to look for tests (or subtests within tests) that span a large age range so that the test is appropriate for both the child’s chronological and developmental age. For example, the Stanford-Binet 5 spans the age range from 2 to 85.  It is also important that the test have an appropriate sampling of easier item content to minimize the floor effect.  It can be beneficial to use tests which build in extended opportunity for teaching the task for children who need extra time to learn how to do the task. For example, the DAS-II has extended opportunity to teach the subtests via corrective feedback. For those children who are not able to complete a full IQ test due to extremely limited attention and energy, it can be helpful to choose a test which has a built in brief Full Scale IQ score.

Match between test and child: When evaluating the appropriateness of a specific test for a specific child, look carefully at the motor, visual, and oral language demands of the test. Are they a good fit for the child? Does the test introduce construct irrelevant bias?  For example, some tests of verbal intelligence require motor responses which would be inappropriate for a child who communicates through spoken language but cannot manipulate objects with their hands. Other verbal intelligence tests require that child to see and respond to pictures, which would be inappropriate for a child who cannot see.

Is it possible to make necessary adaptations without changing the nature of the task? Some tests are not easily adapted for the specific child’s motor, sensory, or language abilities, and thus should not be administered. If a child does not have sufficient motor control to move small blocks, and you move the blocks for the student, that is a modification of the test which changes the nature of the task. If you choose to administer a test with modifications, it would be appropriate to interpret the results qualitatively and not quantitatively.

Sometimes it is appropriate to administer a nonverbal test of intelligence. Nonverbal refers to the method of administration and responses of the examinee, not what is being measured, nor the strategies used to arrive at solutions to questions. In nonverbal tests, children do not need to speak. Sometimes, instructions are also provided completely nonverbally using gestures and facial expression.

Review of IQ/developmental tests in special populations

Commonly used measures of intelligence

• Wechsler Intelligence Scale for Children – 5
• Differential Abilities Scale – II
• Stanford Binet – 5
• Kaufman Assessment Battery for Children – 2
• Reynolds Intellectual Assessment Scales – 2
• Woodcock Johnson Tests of Cognitive Abilities – 4

 Nonverbal measures of intelligence

• Wechsler Nonverbal Scales of Ability
• Leiter International Performance Scale – 3
• Universal Nonverbal Intelligence Test – 2
• Comprehensive Test of Nonverbal Intelligence – 2
• Other nonverbal, single domain tests

Measures of early cognitive development

• Bayley Scales of Infant and Toddler Development – 4
• Batelle Developmental Inventory -2
• Mullen Scales of Early Learning

General intelligence tests

Wechsler Intelligence Scale for Children -5th Edition (WISC-V), 2014 & WISC-V Integrated, 2015

• Age range 6:0 to 16:11
• Benefits:
  • Most common test of IQ in children; is well known.
  • Most subtests can be completed without motor manipulation of items.
  • Has a Nonverbal Index (but this requires the motor ability to do Coding).
  • Q-interactive (iPad administration) makes administration and scoring simple and quick.
  • WISC-V Integrated can be used in conjunction with the WISC-V in order to “break down” the task demands of WISC-5 subtests. WISC-5 Integrated is designed to identify the underlying cognitive processes that may be impairing performance on the WISC-V (e.g., what happens when the child is given extra time, or given multiple choice instead of needing to generate responses).
• Potential drawbacks/considerations:
  • Children with developmental level below 5 or 6 years may have difficulty understanding the task demands of some subtests on the WISC.
  • Only a few subtests are appropriate for children who are completely nonverbal and who do not have use of their hands (Matrix Reasoning, Figure Weights, Visual Puzzles and possibly Picture Span). These subtests would require some adaptation depending on the child’s communication strategies (e.g., use of gestures, eye gaze, etc.)
  • WISC-V Integrated subtests should not be interpreted as measures of IQ. In some cases, it may be appropriate to administer a WISC-V Integrated subtest without first administering the corresponding WISC-5 subtests. For example, if a child is not able to speak, but is able to point or otherwise indicate choices, the verbal multiple choice subtests will give you an idea about the child’s language based knowledge and reasoning. However, WISC-V Integrated scores should never be interpreted as a measure of a child’s intelligence.

Differential Abilities Scale, 2nd Edition (DAS-II), 2007

• Age range 2:6 to 17:11.
• Early years record form: 2:6 to 6:11, out-of-level normative data available for up to age 8:11.
• School-age record form: age 7:0 and up.
• Benefits:
  • Extended opportunities for teaching the tasks.
  • Abbreviated testing time due to special rules for start and stop points.
  • Out-of-level normative data can be very useful for children ages 7 and 8 as they can be administered the young child battery.
  • Some core subtests (Pattern Construction, Matrices, Recall of Digits) as well as quite a few Diagnostic subtests span the entire age range (2:6 to 17:11).
  • For the most part, the DAS does not require motor skills (except for early items on Verbal Comprehension, Copying and Pattern Construction). Other subtests can be easily adapted to give oral responses instead of motor responses (e.g., Picture Similarities).
  • Special Nonverbal Composite (SNC) is a 4 subtest composite, but is not appropriate for children with limited motor function. There is a 2 subtest Nonverbal Reasoning Index that is appropriate for children with limited motor functioning (Upper Level Early Years and School Age).
  • Includes signed nonverbal subtest administration instructions for children who use American Sign Language.
• Potential drawbacks/considerations:
  • Early Years Verbal subtests are inappropriate for children with significant visual impairments, and at the earliest level, inappropriate for children with significant motor impairments.
  • No Canadian normative data.

Stanford Binet – 5th Edition (SB-5), 2003

• Age range 2:0-85+ within a single series of subtests.
• Five areas (Fluid Reasoning, Knowledge, Quantitative Reasoning, Visual Spatial, and Working Memory) are assessed in both the Verbal and the Nonverbal domains.
• Benefits:
  • The fact that all subtests are given to all ages (at the appropriate level) makes this an excellent test for evaluating children whose developmental level is 2+, but whose cognitive functioning is highly discrepant from their age level.
  • Nonverbal routing subtest starts with manipulatives which can be helpful for children who do not understand concepts on paper (such as bigger/smaller).
  • Extensive guidance is provided in the manual on the use of SB-5 in hearing impaired individuals.
• Potential drawbacks/considerations:
  • “Nonverbal” tasks require a fair bit of receptive and expressive language.
  • Some nonverbal tasks cannot be easily modified for individuals with motor impairments.
  • Early verbal tasks require visual inspection of pictures and visual manipulation of objects. Therefore, this limits the utility of this test in children with visual impairments. Adaptations can be made for motor impairments.
  • More difficult to administer than many other standard IQ tests.
  • Age equivalent scores are only available if you give both verbal and nonverbal portions of a domain and for the abbreviated battery.
  • No Canadian normative data.

Kaufman Assessment Battery for Children, 2nd Edition (2004), Normative Update (2018)
(KABC-II NU, 2018)

• Ages 3:0 – 18:11
• Benefits:
  • Comprehensive measure of intellectual functioning designed to minimize verbal instructions and responses and limit “cultural content”.
  • Many subtests span the age range: Atlantis, Face Recognition, Number Recall, Gestalt Closure, Rover, Expressive Vocab, Verbal Knowledge, Rebus, Triangles, Word Order, Hand movements, Riddles.
  • In addition, out of age range norms are available for some ages (e.g.,. a 7 year old can be administered the 5 or 6 year old battery).
  • Extensive teaching is available.
  • Nonverbal scale available at each age point.
  • Most subtests have a sample item plus two teaching items (for children at the youngest age).
• Potential drawbacks/considerations:
  • Most nonverbal subtests require pointing. Some can be adapted with use of a grid (to label response options) but other subtests are not easily adapted in this way.
  • No Canadian normative data.

Reynolds Intellectual Assessment Scales, 2nd Edition (RIAS-2, 2015)

• Ages 3-94
• 4 core intelligence subtests (2 verbal, 2 nonverbal), 2 processing speed (verbal/nonverbal), optional verbal + nonverbal memory subtests
• Benefits:
  • Short administration time.
  • Minimizes need for motor skills.
• Potential drawbacks/considerations:
  • Supplemental subtests are different by age.
  • No Canadian normative data.

Woodcock Johnson Tests of Cognitive Abilities, 4th Edition, (WJ–IV Cognitive)

• Ages 2 +
• 10 core intelligence tests
• Benefits:
  • Low floor.
  • 3 subtest Brief Intellectual Ability score.
  • Co-normed with Woodcock Johnson’s tests of Oral Language and Achievement.
  • Braille & Large Print versions available through American Printing House for the Blind.
• Potential drawbacks/considerations:
  • No Canadian normative data.

Nonverbal scales of intelligence

Wechsler Nonverbal Scales of Ability (WNV), 2006

• Age range – 4:0-21:11
• Ages 4:0-7:11: Matrices, Coding, Object Assembly, Recognition
• Ages 8:0-21:11: Matrices, Coding, Spatial Span, Picture Arrangement
• Benefits:
  • Primarily pictorial/gestural instructions. Can be entirely nonverbal, but verbal instructions are provided.
  • Translations of verbal instructions (and prompts) are provided in 6 languages.
  • Completely nonverbal response format available.
  • There are Canadian norms available.
  • 2 subtest abbreviated scale option.
• Potential drawbacks/considerations:
  • Only 1 of the 4 scales spans the age range, meaning that for the other subtests, there is the issue of floor effects.
  • As an abbreviated measure, it has limited coverage of cognitive abilities.
  • Only 2 subtests (Matrices, Recognition) are easily adapted for those with serious motor disability.

Leiter International Performance Scale, 3rd Edition (Leiter-3), 2013

• Ages 3 to 75
• 4 Cognitive subtests, 4 attention/memory/processing speed subtests
• Benefits:
  • Completely nonverbal assessment. All instructions are conveyed via picture, gesture, and demonstration. There are no oral responses required.
  • All subtests span the age range.
  • The cognitive subtests are untimed and do not require careful placement of cards/blocks so that children with mild motor impairments may be fully capable of completing the tasks.
• Potential drawbacks/considerations:
  • Takes time to learn how to administer the Leiter correctly. There is a training DVD available.
  • The examinee responds by moving small cards or blocks to indicate a response. Some children with severe motor impairments will not be able to do this.
  • In our clinic, we have had the experience that the Leiter-3 sometimes over-estimates a child’s true capabilities. Therefore, we recommend the Leiter should always be administered in conjunction with another IQ test.
  • No Canadian normative data available.

Universal Nonverbal Intelligence Test, 2nd Edition (Unit-2), 2016

• Age 5:0-21:11
• 6 subtests: Symbolic Memory, Nonsymbolic Quantity, Analogic Reasoning, Spatial Memory, Numerical Series, and Cube Design.
• Benefits:
  • Entirely nonverbal administration and response format.
  • Has a 2 subtest brief IQ score available.
  • Attempts to limit cultural content.
• Potential drawbacks/considerations:
  • 3 of the 6 subtests require the child to manipulate task materials.
  • One subtest (Cube Design) is timed, with no option for an untimed administration. This subtest is not appropriate for those with severe motor impairments.
  • All other subtests require pointing to the correct response or moving tiles. This could be adapted to place letters/numbers below the responses for those who cannot point.
  • Some subtests are reliant on the child understanding written numbers and having a basic understanding of numbers (e.g., counting by 5s).

Comprehensive Test of Nonverbal Intelligence, 2nd Edition (C-TONI-2), 2009

• Ages 6:0-89-11
• 6 subtests: Pictorial Analogies, Geometric Analogies, Pictorial Categories, Geometric Categories, Pictorial Sequences, Geometric Sequences.
• Benefits:
  • Can be entirely nonverbal administration, but verbal instructions are also provided.
  • Response format does not require any verbal output.
  • No manipulation of objects required.
  • Completely untimed.
• Potential drawbacks/considerations:
  • All subtests require pointing to the correct response. This could be adapted to place letters/numbers below the responses for those who cannot point.
  • No measurement of short term or working memory.

Single domain nonverbal tests

These are single domain tests of intelligence. Although they are quick and easy to administer, they are not generally appropriate as stand-alone diagnostic tests of IQ. They may be appropriately used in conjunction with another IQ test.

• Raven’s Progressive Matrices (Various). Child/Adult.
• Naglieri Nonverbal Ability Test (2003). Age 5:0-17:11.
• Test of Nonverbal Intelligence–4th Ed. (2010). Age 6:0-89.

Developmental Measures

These are standardized measures which provide information about a child’s developmental status by assessing specific developmental milestones. Use of a developmental measure in an older child can be a good way to provide a structure to your assessment of developmental level.

Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-4, 2019)

• Ages: 1 to 42 months (3 years, 6 months)
• Three scales administered with child interaction – cognitive, motor, language. Two scales conducted with parent questionnaires – social-emotional, adaptive behavior.
• Cognitive scale benefits:
  • Play-based test with natural type interactions.
  • Administration manual discusses accommodations/modifications.
  • Allows for some items to be scored based on parent report.
• Cognitive scale potential drawbacks/considerations:
  • Takes some time to learn to administer.
  • Starting from 13 months – requires the child to follow verbal instructions.
  • Requires some motor coordination from child (cannot modify some items for lack of hand use).
  • No Canadian normative data.

Batelle Developmental Inventory -2nd Ed., Normative Update (Batell-2-NU; for the 2015 US census)

• Tests 5 global developmental domains and 13 subdomains: Adaptive behaviour, personal and social skills, motor skills, communication skills, and cognitive.
• Ages 0 – 7:11
• Benefits:
  • Wide age range for a developmental measure
  • Play-based test with natural type interactions.
• Potential drawbacks/considerations:
  • Challenging to learn and to administer
  • No Canadian normative data

Mullen Scales of Early Learning – 1995

• Birth to 68 months
• Benefits:
  • Play-based test with natural type interactions.
• Potential drawbacks/considerations:
  • Challenging to learn and to administer
  • No Canadian normative data
  • Older normative data

Recommendations

How do you choose which measure of intelligence or development to use in an assessment?  You are looking for the best match between the child’s capabilities and the tests’ ability to capture those capabilities. The Wechsler scales (WPPSI, WISC, WAIS) may be a perfectly appropriate measure to use with children who have moderate (and sometimes even severe intellectual disabilities).  However, what if the child does not understand the tasks, or is not able to respond due to motor limitations? The first choice would be to choose a measure that is both developmentally AND age appropriate. For children who are developmentally 3 or over, the DAS-2 or the KABC-II are excellent choices as they are comprehensive measures where each subtest has relatively discrete demands. However, for younger children, the motor and visual demands on the verbal subtests of the DAS may make it inappropriate. For those children (with adequate vision and hearing) who are are able to complete developmental tasks at the age 2 to 3 year old level , the Stanford Binet-5 is an excellent option.

When you have a child who shows some capability to do standardized testing but who has extremely limited ability to participate due to limited attention, energy, etc., the following are some options for abbreviated scores which can provide an estimate of IQ:

• SB-5 two subtest abbreviated IQ
• WNV two subtest abbreviated IQ
• Peabody Picture Vocabulary Test (PPVT) as estimate of IQ

Although important for addressing the diagnostic question of an intellectual disability, the results of a standardized test for children with severe disabilities can be of limited functional value. For a 14 year old who is functioning on a test at a 2 year old level or less, your standard scores, even for those tests with “low floors” will be at the “floor” of the test… so what to do? Document the low score – it may be necessary for access to services. Next, describe what the child “can do.” For example, Sammy was able to objects match by shape or color, but did not understand simple pattern reasoning (e.g., XOXO?). For those children who appear to be under approximately age 2 developmentally, consider doing a developmental assessment of functioning (e.g., Bayley-4) to get a more objective measure of their developmental level. Interpret age equivalent (AE) scores, but see caution.