Marked Intraindividual Cognitive Variability in a Sample of Healthy Graduate Students

In this pilot study, intraindividual variability in neurocognitive test performance was examined in 24 healthy individuals with high levels of education and average full-scale IQ of 121.9 on a short neuropsychological battery across multiple cognitive domains. Marked variability was found across all domains. Intraindividual differences between the highest and lowest z-scores ranged from 2.05 to 6.92 (M = 3.89, SD = 1.25). Based on the definitions of abnormality proposed by Lezak, Wechsler and Heaton, 46% of our sample participants had at least one score that was more than 2 standard deviations below the population mean; 50% had at least one score that was less than the 5th percentile (z  1.0 SD) across our sample. Our findings suggest the need for caution when inferring the presence of cerebral dysfunction in high academic achievers, particularly in a medical legal setting where false-positive diagnoses may be of particular consequence.