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Iskandar S, Murphy KJ, Baird AD, West R, Armilio M, Craik FIM, Stuss DT. Interacting effects of age and time of day on verbal fluency performance and intraindividual variability. AGING NEUROPSYCHOLOGY AND COGNITION 2015; 23:1-17. [PMID: 25827792 DOI: 10.1080/13825585.2015.1028326] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
We explored the effects of age and time of day (TOD) on verbal fluency ability with respect to performance level and intraindividual variability (IIV). Verbal fluency, which involves complex cognitive operations, was examined in 20 older (mean age = 72.8 years) and 20 younger (mean age = 24.2 years) adults with test start time alternating between morning and evening across four days. Older adults generated more words in the morning and younger adults more in the evening, corresponding with self-report peak TOD. Age by TOD interactions were also observed across fluency tasks on the number of switches among subcategory exemplars during word generation and on the IIV observed in switching behavior. Older adults exhibited greater variability in switching in the evening than in the morning, whereas younger adults showed the opposite pattern. These findings demonstrate that processes involving energization (initiating and sustaining) and attentional control may be particularly sensitive to age differences in TOD influences on cognition.
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Affiliation(s)
- Sam Iskandar
- a Psychology Department , University of Windsor , Windsor , ON , Canada
| | - Kelly J Murphy
- b Psychology Department , Baycrest , Toronto , ON , Canada.,c Psychology Department , University of Toronto , Toronto , ON , Canada
| | - Anne D Baird
- a Psychology Department , University of Windsor , Windsor , ON , Canada
| | - Robert West
- d Psychology Department , Iowa State University , Ames , IA , USA
| | - Maria Armilio
- e Credit Valley Neuropsychology Group , Toronto , ON , Canada
| | - Fergus I M Craik
- c Psychology Department , University of Toronto , Toronto , ON , Canada.,f Rotman Research Institute , Baycrest & University of Toronto , Toronto , ON , Canada
| | - Donald T Stuss
- c Psychology Department , University of Toronto , Toronto , ON , Canada.,f Rotman Research Institute , Baycrest & University of Toronto , Toronto , ON , Canada.,g Ontario Brain Institute , Toronto , ON , Canada
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