Developmental and Cognitive Assessment: Bayley-4 and WISC

An inseparable part of an ASD assessment is measuring the child's cognitive/intellectual capacity with standard tools. This information is needed both to determine the presence of an accompanying intellectual disability (see Chapter 13) and to personalize educational and treatment planning.

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

The Bayley-4 is a hands-on developmental test that assesses cognitive, language, motor, social-emotional, and adaptive behavior areas in infants and young children from birth to 42 months. It is administered through structured tasks using age-appropriate toys and materials, and it provides a developmental age and standard score for each area. In this early age group, the Bayley-4 is a key tool both as part of the ASD assessment and in determining the degree of general developmental delay.

Wechsler Intelligence Scale for Children (WISC)

In older children (typically age 6 to 16), the current edition of the Wechsler Intelligence Scale for Children (WISC-V) separately assesses the subareas of verbal comprehension, visual-spatial reasoning, fluid reasoning, working memory, and processing speed. The profile of these subarea scores carries far more clinical information than a single overall IQ score.

Did You Know? — Why Does the Subarea Profile Matter?

In many children with ASD, there is a marked spread ("scatter") among the WISC subareas: for example, visual-spatial reasoning may be strong while verbal comprehension or processing speed comes out markedly lower. This pattern of scatter is a far richer source of information than a child's single overall "IQ score," and it guides the choice of educational strategies suited to the child's learning style (see Chapter 25).

Cognitive Assessment in Nonverbal or Minimally Verbal Children

In children with limited or no spoken language, standard verbally-weighted tests can give misleading results; in this case, experienced psychologists give more weight to visual-spatial and performance-based subtests (for example, entirely nonverbal tests like the Leiter International Performance Scale). This is critical to keep a nonverbal child's intellectual capacity from being wrongly underestimated simply because of difficulty with verbal expression.

When to Seek Advice

Administering only a verbally-weighted test to a child with limited spoken language and concluding "intellectual disability" can be a serious assessment error. Make sure your child's assessment also uses nonverbal/performance-based tests.

Using the Assessment Results

Cognitive assessment results are used in preparing the individualized education plan for school (see Chapter 33), in setting therapy goals in a way that suits the child's cognitive capacity, and in monitoring development over time (usually by repeating the assessment every 2 to 3 years). A single assessment is not a "permanent label"; the profile can change as the child develops.