Abstract
BackgroundIntra-individual variability in reaction time (RT IIV) is considered to be an index of central nervous system functioning. Such variability is elevated in neurodegenerative diseases or following traumatic brain injury. It has also been suggested to increase with age in healthy ageing.ObjectivesTo investigate and quantify age differences in RT IIV in healthy ageing; to examine the effect of different tasks and procedures; to compare raw and mean-adjusted measures of RT IIV.Data SourcesFour electronic databases: PsycINFO, Medline, Web of Science and EMBASE, and hand searching of reference lists of relevant studies.Study EligibilityEnglish language journal articles, books or book chapters, containing quantitative empirical data on simple and/or choice RT IIV. Samples had to include younger (under 60 years) and older (60 years and above) human adults.Study Appraisal and SynthesisStudies were evaluated in terms of sample representativeness and data treatment. Relevant data were extracted, using a specially-designed form, from the published report or obtained directly from the study authors. Age-group differences in raw and RT-mean-adjusted measures of simple and choice RT IIV were quantified using random effects meta-analyses.ResultsOlder adults (60+ years) had greater RT IIV than younger (20–39) and middle-aged (40–59) adults. Age effects were larger in choice RT tasks than in simple RT tasks. For all measures of RT IIV, effect sizes were larger for the comparisons between older and younger adults than between older and middle-aged adults, indicating that the age-related increases in RT IIV are not limited to old age. Effect sizes were also larger for raw than for RT-mean-adjusted RT IIV measures.ConclusionsRT IIV is greater among older adults. Some (but not all) of the age-related increases in RT IIV are accounted for by the increased RT means.
Highlights
Intra-individual variability in reaction time (RT IIV)—generally understood as the variability of the responses of one individual on a single test within a single testing occasion—is often reported to increase with age in adulthood [1]–[4]
For all measures of RT IIV, effect sizes were larger for the comparisons between older and younger adults than between older and middle-aged adults, indicating that the age-related increases in RT IIV are not limited to old age
RT IIV is greater among older adults
Summary
Intra-individual variability in reaction time (RT IIV)—generally understood as the variability of the responses of one individual on a single test within a single testing occasion—is often reported to increase with age in adulthood [1]–[4]. The available empirical evidence supports this notion, in that greater RT IIV is observed in a number of conditions affecting the CNS; for example, in neurodegenerative diseases (Alzheimer’s or Parkinson’s Disease [6]) or following a traumatic brain injury [7], [8]. RT IIV is associated with white matter integrity in otherwise healthy adults [12]. Taken together, this evidence suggests that increased RT IIV marks a deterioration of the CNS functioning. Intra-individual variability in reaction time (RT IIV) is considered to be an index of central nervous system functioning. Such variability is elevated in neurodegenerative diseases or following traumatic brain injury. It has been suggested to increase with age in healthy ageing
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