Although there is work suggesting that ISV may be reliable, albeit less so than measures of central tendency, this work is restricted to a small number of metrics. It remains unknown how other measures, such as ex-Gaussian and LATER parameters, compare to more common measures like standard deviations and coefficients of variation.
One determining factor of the reliability of ISV is the number of trials it is based upon. According to the Spearman–Brown formula (Brown, 1910; Spearman, 1910), the Gaussian distribution of error variance leads to error cancelling itself out with increasing aggregation of data, leaving the true score intact.