The examiner must select either the Luria or CHC model before testing the child or adolescent, thereby deciding whether or not crystallized ability should be considered as an aspect of the individual’s general cognitive ability and determining which one of the two global scores will be used to summarize the present level of functioning of each 3- to 18-year-old referred for assessment.

The authors have followed a fundamental principle for all their tests, clearly stated in their test manuals: measures of Gc should be excluded from any score that purports to measure a person’s intelligence or overall cognitive ability whenever the measure of Gc is not likely to reflect that person’s level of ability. The principle is central to the following recommendations regarding choosing the global score to use for the KABC-II.

The CHC model should generally be the model of choice, except in cases where the examiner believes that including measures of acquired knowledge/crystallized ability would compromise the validity of the Fluid-Crystallized Index (FCI). In those cases, the Luria-based global score (MPI) is preferred. The CHC model is given priority over the Luria model because the authors believe that Knowledge/Gc is, in principle, an important aspect of cognitive functioning.

Cases where the Luria model (MPI) would be preferred include, but are not limited to, the following:

• a child from a bilingual background
• a child whose non-mainstream cultural background may have affected knowledge acquisition and verbal development
• a child with known or suspected language disorders, whether expressive, receptive, or mixed receptive-expressive
• a child with known or suspected autism
• a child who is dear of hard of hearing

In addition, an examiner with a firm commitment to the Luria processing approach, who believes that acquired knowledge should be excluded from any global cognitive score (regardless of the reason for referral), may use the KABC-II in the same way as the original K-ABC, as a Luria-based instrument.

The CHC model is recommended for most other situations, including evaluation of children with the following known or suspected conditions: disability in reading, written expression, or mathematics; mental retardation; attention deficit hyperactivity disorder, or emotional/behavioral disturbance. The CHC model is particularly appropriate for assessing children for entry into programs for the gifted and talented; because such programs typically emphasize academic (Gc) skills, and because crystallized ability tends to be a strength of gifted children, the CHC model is fairer and more suitable for this application.

This set of recommendations does not imply that one model is considered theoretically superior to the other. Both theories are equally important as foundations of the KABC-II. The CHC psychometric theory emphasizes specific cognitive abilities, whereas the Luria neuropsychological theory emphasizes “processes,” namely the way children process information when solving problems. Both approaches are valid for understanding how children learn and solve new problems, which is why each scale has two names, one from each theory.

And the way in which psychologists interpret the scales will likely be influenced by their theoretical preference. Examiners who are more comfortable with the CHC approach to cognitive abilities than with the Luria system of functional units will, naturally, interpret the KABC-II scales from the vantage point of the CHC broad abilities, even if they choose to report the MPI as the global measure of cognitive functioning for a particular child who, for example, is suspected of having a language disorder. Likewise, a Luria-oriented examiner may interpret the scales from the perspective of the three functional units even if they opt to interpret the FCI for a verbally gifted child or adolescent. The interpretive approach that examiners apply to the child’s scale profile is less important than the decision they make regarding which global score to interpret, which should be based on referral and background factors.

For further information see the CHC and Luria Theories: Understanding and Selecting the Appropriate Model video.K