Abstract
Testing cognitive skill development is important for diagnostic, prognostic, and monitoring purposes, especially for young children and individuals with neurodevelopmental disorders. Developmental tests have been created for infants and toddlers, while traditional IQ tests are often employed beginning in the later preschool period. However, IQ tests rely on developmental skills that are rapidly changing during early childhood. Here, we introduce the idea of prerequisite skills in developmental domains, which are discrete skills required for, but not explicitly tested by, traditional IQ tests. Focusing on general cognition, particularly among children with a chronological or mental age under 4 years, may fail to capture important nuances in skill development. New skill-based assessments are needed in general, and in particular for categorization, which is foundational to higher-order cognitive skills. Novel measures quantifying categorization skills would provide a more sensitive measure of development for young children and older individuals with low developmental levels.