The aims of the present study are therefore threefold. Firstly, we set out to derive a large set of different ISV metrics from standard neuropsychological tasks that are popular in clinical research and explore the relationships between these measures. Are different measures of ISV redundant with regard to each other, or do they offer different information? Secondly, we determined the instrumental (odd–even) and test–retest reliabilities of these measures to assess their appropriateness as trait correlates in differential research. Which measures of ISV are most reliable? Finally, we conducted a Monte Carlo analysis of the test–retest reliability of the mean and standard deviation of RTs with different numbers of trials. Is the increase in reliability that the Spearman–Brown formula predicts with increasing trials slower for ISV than mean RT?