Aging and inhibitory errors on a motor shift of set task.

Inhibitory functions are key mechanisms underlying age-related cognitive decline (Park and Gutchess in Cognitive aging: a primer, Psychology Press, Hove 2000), yet how these influence the control of action has not been fully investigated. Using 134 older (age 60-88) and 133 younger adults (age 20-59), we investigated in a motor analogy of the WCST the inhibition of a primed movement plan in favour of a novel one. Although 10% of older adults performed similarly to young adults, the majority failed to inhibit by the sixties, 10-20 years earlier than documented for the WCST (Lezak in Neurological Assessment, Oxford University Press, New York 1995; Haaland et al. in J Gerontol 33:345-346 1987). Around 40% failed to learn on the second attempt, and of these, the majority in their sixties to eighties failed to learn eventually. Implications are discussed for neuropsychological theory and everyday interventions.