Unlocking the potential: validity evidence for a comprehensive developmental assessment in children and adolescents

In psychological research and practice, test procedures that assess children’s and adolescents’ developmental domains play a fundamental role as they serve a variety of important purposes. For example, practitioners such as school psychologists base their high-stakes diagnostic decisions and recommendations for future schooling support measures on the results of these instruments. To ensure accurate interpretations of scores obtained from such test procedures, their validity needs to be corroborated. At the same time, a holistic assessment of the core developmental domains (i.e., cognitive abilities, psychomotor skills, social-emotional skills, cultural skills, noncognitive personality characteristics) is integral to enabling an in-depth understanding of children’s and adolescents’ unique strengths and areas of development. In the pursuit of extending current knowledge on validity evidence and contributing to a comprehensive developmental assessment of children and adolescents, the current cumulative dissertation aims to provide insights on three validity aspects of test scores from the Intelligence and Development Scales (IDS) and the Intelligence and Development Scales–2 (IDS-2). Following this goal, three studies were conducted that analyzed (1) differential validity for a clinical subgroup of autistic individuals, (2) criterion validity for multi-informant academic achievement in typically developing individuals, and (3) the contribution of participant characteristics, in particular aspects of proficiency in the test language, to test performance, which may interfere with the validity of score interpretations in individuals at risk for linguistic disadvantages.
Samples consisting of children and adolescents aged between 5 and 20 years drawn from the IDS and IDS-2 standardization and validation studies and from additional validation studies were investigated with independent-samples t tests, structural equation modeling analyses, and hierarchical regression analyses. Results of the first study demonstrated the differential validity of test scores in psychomotor skills, language skills, and externally rated achievement motivation of the IDS-2 for autistic children and adolescents and showed that group differences in some developmental domains (e.g., social-emotional skills) may be dependent on factors such as age. The second study provided evidence on the criterion validity of IDS and IDS-2 intelligence scores for multi-informant academic achievement. Moreover, it revealed the incremental role of noncognitive personality characteristics, such as traits and motives, in predicting most of the objective and subjective academic achievement measures. Last, the third study uncovered the contribution of proficiency in the test language as a critical participant characteristic in the assessment of the IDS-2 domains. The findings suggested that the relative importance of different language aspects depends mainly on the verbal demands of the presented tasks.
In conclusion, the present work provides evidence on the validity of test scores from two comprehensive test batteries across different groups of children and adolescents and contexts. In addition, this dissertation highlights the need for a fine-grained view in the process of validating test procedures, offers conclusions on practical implications, and supports a holistic assessment of children’s and adolescents’ various developmental domains to ensure that the full potential of the individual is captured and unlocked.