Neurocognitive assessments are fundamental for modeling human development. The proposition of this article is that insights from both theory and neuroscience can mutually advance each other, and both can serve as reciprocal tools for constructing improved assessments. Children begin with an abundance of neurons at birth and evolve into sophisticated problem solvers. Grounded in historical perspectives shaped by classic figures such as Ramon y Cajal, Binet, and Piaget, this article delves into the developmental theory of constructive operators. It integrates ideas from psychological theory and neuroscience findings. Four guiding principles emerge that can help steer the course of developmental cognitive neuroscience (i.e., age groupings, child-friendly and culture-appropriate assessments, and meta-subjective task analysis). These principles underscore the benefits of employing theoretically based measures that highlight cognitive potential in complement to learning outcomes and have applications both behaviorally and in neuroimaging. This strategic approach holds considerable promise for driving progress in science, education, clinical practice, and policymaking.