Refining cognitive dispersion metrics for brain–behavior prediction in aging and mild cognitive impairment

INTRODUCTION This study addresses three key issues in the standardization of cognitive dispersion: its operationalizations though intra‐individual standard deviation (ISD) versus coefficient of variation (CoV), its reliability, and its dependence on the size of the neuropsychological battery. METHODS Cognitive dispersion was calculated in 318 older adults (M age = 70.7, 61% female). Linear regression tested whether ISD, in the context of mean cognitive performance, provided greater explanatory power than CoV for brain morphometry. We further evaluated 2‐year reliability of dispersion and compared psychometric properties across four battery sizes. RESULTS We found that ISD, modeled jointly with mean cognitive performance, was a stronger predictor of entorhinal cortex thickness than CoV, which obscured critical mean–dispersion interactions. DISCUSSION These findings suggest that ISD, rather than CoV, offers a more valid quantification of cognitive dispersion, and that dispersion measures are most informative when derived from adequately comprehensive neuropsychological batteries.