Cognitive flexibility in aging: the impact of age range and task difficulty on local switch costs in task switching.

Introduction: Previous studies provided inconclusive results regarding the effects of aging on the ability to flexibly switch between task rules (local switch cost). The goal of the present study was to investigate the influence of age on the local switch costs at two levels of difficulty (easy task switching: two task rules vs. difficult task switching: four task rules). Methods: The local switch costs, i.e., reaction time and error differences between trials with a task switch and task repetition relative to the previous trial, were compared in a group of young adults (19 to 33 years) and three groups of older adults (64-72; 73-80; 82-97 years). Results: The analysis of the switch costs showed significantly higher switch costs of the three groups of older adults compared to the younger adults and the effect was more pronounced in the difficult task switching than in the easy task switching. At the same time, there were no clear differences in the local switch costs between the three groups of older adults. Discussion: The results showed that even after the age-related slowdown was taken into account, age differences in local switch costs will emerge when the age range of older adults is extended and task difficulty is sufficiently high. These findings contribute to our understanding of how and when age differences in cognitive flexibility emerge and suggest that complex multitasking environments may disproportionately challenge older adults.