Problem: As with any study, several limitations must be considered when interpreting the present results. First, it remains unclear as to why the matrices corresponding to the normative data for participants ages 5-6 and 13-16 failed to converge in EFA. As singularity is often the default source when a matrix is found to be non-positive definite and unable to be inverted (Lorenzo-Seva & Ferrando, 2021), we again inspected the values in the matrices though were unable to identify any coefficients that appear to be offending. It is worth noting that inspection of the normative conversion tables in the Clinical Manual (Korkman et al., 2007a, b, c) reveal inadequate item density and ceiling effects in several of the NEPSY-II measures at ages 13-16. Thus, it is possible that this restricted scaling may have led to the collapse in latent dimensionality in the measure at that age. It is also worth disclosing that the decision to extend the age range for the test was made post-hoc after preliminary pilot studies were completed and does not appear to be part of the original design plan. Nevertheless, due to the inability to examine the factor structure of the instrument at those ages, it remains unclear as to whether the differences in dimensional complexity observed across the age range are due to developmental differences in the growth and emergence of higher-order abilities (as postulated by Tucker-Drob, 2009) or an artifact of differential measurement-effects across the age range. Need Assignment Help?