Development and Validation of Norm-Referenced Measures of Reaction Time Inconsistency




Brewster, Paul W. H.

Journal Title

Journal ISSN

Volume Title



Objective: The purpose of this dissertation was to determine whether measures of reaction time inconsistency (RTI) can be applied clinically to detect cognitive impairment in older adults. Methods: Data were obtained from the Victoria Longitudinal Study (VLS), a longitudinal study of healthy aging, and PREVENT, a multivariate study of risk factors for Alzheimer’s disease. Study 1 examined effects of task complexity and computational approach on the association between RTI and physical and cognitive functioning in participants of the VLS. Study 2 assembled normative data from the VLS and standardized RTI data from an independent VLS cohort against these normative data. Significant Study 1 findings were replicated in Study 2 using the obtained RTI T-Scores, and the clinical utility of results were evaluated using stratum specific likelihood ratios (SSLRs). Study 3 replicated Study 2 analyses in data from PREVENT. Results: Results of Study 1 identified four operationalizations of RTI from a choice reaction task that yielded consistent significant associations with cross-sectional cognitive performance. Consistent associations were not observed between these scores and cognitive change or performance on measures of physical functioning. Study 2 replicated Study 1 findings in an independent sample using RTI T-Scores. SSLRs supported the clinical utility of measures of RTI for detecting prevalent cognitive impairment. Study 3 replicated findings from Study 2, but SSLRs indicated that only low RTI scores yielded associations of sufficient reliability for clinical interpretation. Consistent with Study 1 and Study 2, associations between RTI T-Scores and measures of physical function were nonsignificant. Conclusions: Low RTI T-Scores were shown across two samples to be associated with a clinically meaningful reduction in the odds of cognitive impairment. Further research is needed in order to clarify the utility of high RTI scores for positive prediction of cognitive impairment.



Aging, Reaction time, Intraindividual variability, Psychometrics, Cognitive impairment