Factor structure of the VABS-3 Comprehensive Parent/Caregiver form in autistic individuals: Poor fit of three-factor and unidimensional models.

Adaptive behavior is a broad set of skills needed to function in everyday life. The Vineland Adaptive Behavior Scales (VABS-3) is commonly used to measure adaptive behavior. It divides adaptive behavior into three domains, Communication, Daily Living Skills, and Socialization, each of which are split into subdomains. Analyses of this three-part structure of the first version of VABS used the instrument as an interview, but now it is done as a questionnaire as well. The structure has not been well supported in samples of autistic people, who often have different strengths and challenges in adaptive behavior compared with non-autistic people. Because adaptive behavior is an important concept in autism research and online-administered questionnaires are increasingly common, it is important to ensure the structure of the VABS-3 Comprehensive Parent/Caregiver Form (VABS-3:CPCF; a questionnaire) works well for autistic individuals across a range of abilities. This study aimed to investigate whether VABS-3:CPCF measures adaptive behavior similarly in verbal and minimally verbal autistic people. However, the data didn't fit the structure in the first step of the analysis, so this could not be investigated. The next analyses also found the three-domain structure didn't fit in different age and language groups. In addition, the data didn't fit a structure combining all the domains into 1 (unidimensional). These results suggest that neither the three-factor or unidimensional structure fit the VABS-3:CPCF, cautioning against interpretation of domain or overall adaptive behavior composite scores in autistic individuals and further encouraging careful consideration of administration format.