Aging and intraindividual variability in performance: analyses of response time distributions

Area of Science:

• Cognitive Psychology
• Neuroscience
• Gerontology

Background:

• Older adults often exhibit greater performance variability than younger adults.
• This variability is hypothesized to stem from increased attention or intention lapses.

Purpose of the Study:

• To investigate the relationship between age, reaction time (RT), and intraindividual variability.
• To determine if older adults' increased variability is due to attentional lapses.

Main Methods:

• A same-different judgment task was administered to 9 young and 9 older adults over nearly 2000 trials each.
• Reaction time distributions were analyzed using quantile-quantile plots and ex-Gaussian/Weibull function fitting.

Main Results:

• Older adults were slower and more variable than younger adults.
• When reaction time differences were controlled, older adults showed similar or less variability.
• No consistent evidence supported increased skewness in older adults' RT distributions.
• A positive linear relationship was found between average RT and intraindividual variability across all participants.

Conclusions:

• Greater performance variability in older adults may primarily reflect their slower average reaction times.
• A general law may govern the relationship between average reaction time and variability.
• Evidence does not consistently support age-related increases in attentional lapses as the cause of greater variability.