Experimental Factor Ontology term EFO_0009702 (intra-individual reaction time variability measurement) is quantification of the variability in reaction time (the interval of time between the presentation of a stimulus to a subject and the beginning of the subject's response to that stimulus) of an individual, over successive tasks. An increase in intra-individual reaction time variability is a hallmark of neurocogintive disturbance in many neurological and psychiatric disorders, particularly ADHD. Also known as: IIRTV measurement, intra-individual response time variability measurement.