Spared Within-Hands but Impaired Between-Hands Response Preparation in Aging

Older people can use advance information to prepare a subset of finger responses. It is debated, however, whether aging affects the preparation of finger responses on two hands (between-hands preparation) more strongly than the preparation of finger responses on one hand (within-hands preparation). The present study examined the role of temporal uncertainty in this issue. We asked a group of young and older participants to perform a finger-cuing task with four preparation intervals (2, 3, 4, and 5 s), presented either separately in distinct blocks of trials (fixed design: no temporal uncertainty) or randomly intermixed across trials (mixed design: temporal uncertainty). Reaction time and error rates revealed age equivalence for within-hands preparation but an age-related difference for between-hands preparation, regardless of how the preparation intervals were presented. These findings demonstrate a robust, structural difference in the maximal preparation benefit that older adults can achieve when preparing two fingers on two hands but not on one hand. These outcomes are discussed in terms of several theories of cognitive aging.