Examining intraindividual variability in neuropsychological test performance: Implications for identifying cognitive impairment and tracers of invalidity.

< .001, η² = 0.31) significantly differed across groups. Results showed that high levels of variability followed increasing severity of cognitive impairment (i.e., no neurocognitive disorder < mild neurocognitive disorder < major neurocognitive disorder); performance invalidity was also associated with high variability. Additional analyses highlighted CoV as a more robust indicator of prediction utility than individual standard deviation. Overall, findings suggest that use of IIV-d metrics, particularly CoV, differentiates level of cognitive impairment. Performance invalidity can also be identified in some cases, although differentiating invalid responding from major neurocognitive disorder is more challenging using IIV-d metrics alone. Ongoing research is warranted for better understanding the use of IIV-d in facilitating diagnostic clarification and determining whether this method provides incremental value beyond other methods. (PsycInfo Database Record (c) 2026 APA, all rights reserved).