Date Published: March 21, 2019
Publisher: Public Library of Science
Author(s): Lauren M. Potter, Madeleine A. Grealy, Daniel Casasanto.
Action errors can put older adults at risk of injury. Our study is the first to investigate whether older adults are more prone than younger adults to making ‘ironic’ motor errors (i.e., actions they have been instructed not to perform), or over-compensatory motor errors (e.g., moving more to the right when instructed not to move to the left). We also investigated whether error patterns change under cognitive load, and assessed whether age effects in the ability to inhibit a prohibited action are comparable to the age decrements found in the ability to inhibit a natural perception-action coupling in the Simon task. Sixty-four older (Mean = 70.64 years, SD = 5.81) and 39 younger (Mean = 28.74 years, SD = 16.39) adults completed an avoidant instruction line-drawing task (with and without cognitive load), and the Simon task. Older adults showed significantly slower inhibition times than younger adults on the Simon task, as expected, and in line with previous research. Surprisingly, however, older adults outperformed younger adults on the avoidant instruction task, producing fewer ironic and over-compensatory errors, and they performed similarly to the younger adults under cognitive load. Age-related decrements on the Simon but not the avoidant instruction task suggests that the two different types of motor tasks involve different subtypes of inhibition which likely recruit independent cognitive processes and neural circuitry in older age. It is speculated that the older adults’ superior ability to inhibit a prohibited action could be the result of age-related changes in distractibility.
As we age we experience declines in cognitive  and motor  abilities but relatively little is known about how these changes interact to affect the performance on daily activities. Cognitive resources are fundamental to all levels of action control, from perceiving [3–4] and planning [5–6] even basic actions to generating and maintaining normal and consistent movement patterns , and whilst the literatures on cognitive and motor ageing have expanded rapidly they have done so largely independently leaving gaps in our knowledge about the interplay between the two. This is particularly true for the inhibitory processes that are fundamental to both cognitive functioning  and goal directed action .
Similar to previous studies [30–34] older participants showed significantly longer inhibition times than younger participants on the Simon task even after accounting for age-related slowing. Older adults thus showed age-related decrements in both processing speed and the ability to inhibit a natural perception-action response. Unexpectedly however, older adults outperformed younger adults on the avoidant instruction task; when instructed not to move in a certain direction, older adults made significantly fewer ironic errors and the magnitude of their errors was also smaller than younger adults. There were no significant age differences in the percentage or magnitude of over-compensatory errors indicating that overall the older adults were surprisingly better at coping with the error-provoking instructions compared to younger adults.