The clinical practice of child neuropsychology requires making conclusions regarding the relationship between obtained summary scores for verbal, nonverbal and adaptive functioning. Ideally, preschool assessments predict meaningful information about the young child’s future capacity, however, it is unclear whether the interrelationship of these broad functional domains remains the same. In Heffelfinger et al (submitted) a one-factor solution provided the best fit and explained the verbal, nonverbal, and adaptive summary score data in a clinical sample of preschool age. The one-factor solution was the best fit for children with cognitive functioning below and above 70, children under 36 months and 36-72 months, and children with or without medical and neurological disorder. As a confirmatory analysis, a longitudinal measurement invariance analysis was conducted of the main level factor model in a longitudinal subset of the preschool sample. It was hypothesized that the relationship between verbal, nonverbal and adaptive summary scores earlier in life would be significantly invariant, or similar, with the relationship between verbal, nonverbal and adaptive summary scores at re-evaluation after 8 years of age.

A subset of 60 children who underwent repeat neuropsychological assessment at age 8 or older (M = 12.4 years, SD = 2.9 years, range = 8.0 to 17.8 years; 69.3% male; 74.2% white) were included in longitudinal analyses. Initial evaluations occurred between the ages of 6 and 71 months in the Preschool and Infant Neuropsychological Testing (PINT) Clinic. Pearson correlations were computed to assess the relationship between verbal, nonverbal, and adaptive functioning at the two assessment time points. Longitudinal measurement invariance (i.e., psychometric equivalence) was assessed using the alignment method to estimate invariance of the main level factor structure across the two assessment time points.

Functioning during preschool-aged assessment was significantly and moderately correlated with functioning in later childhood or adolescence for verbal intellectual functioning (r = .66, p < .001), nonverbal intellectual functioning (r = .47, p = .001), and adaptive functioning (r = .58, p < .001). When examining longitudinal invariance of the main level factor model, both configural invariance (“weak invariance”) and metric invariance (“strong invariance”) were found for verbal and non-verbal intellectual functioning. However, configural non-invariance was found for adaptive functioning, suggesting that the pattern of loadings for adaptive functioning differed at Time 2 compared to Time 1. The Average Invariance Index is interpreted like a multiple R², with a value close to 1 implying high invariance and a value close to 0 implying low invariance. Average Invariance Index = 0.79, suggesting a relatively high degree of confidence with which mean scores on verbal and nonverbal intellectual functioning can be compared over time.

While the standard scores are all highly correlated across ages, the latent relationship between adaptive and verbal/nonverbal intelligence scores is not the same in preschool as older childhood assessment, suggesting that the interpretation of how adaptive functioning relates to verbal and nonverbal functioning should be considered differently across the ages.