Age differences in the selection of mental sets: The role of inhibition, stimulus ambiguity, and response-set overlap

Switching between tasks leads to response-time (RT) costs at switch points (local switch costs) and often to RT costs at no-switch transitions that oc cur in the context of a task-switching block (global set-selection costs). With trial-to-trial cuing of tasks, moderate age effects were obtained for local switch costs, but large age effects were obtained for global selectio n costs. In Experiment 1, set-specific inhibition was found to be at least as large in old as in young adults, thus ruling out an inhibition deficit a s a reason for age differences in global costs. In Experiment 2, large age differences in global costs were limited to conditions of ambiguous stimuli and full response-sct overlap. This pattern of results suggests a greater reliance on set-updating processes in old than in young adults. The role of these processes is to ensure unambiguous internal control settings when am biguity arises from stimuli and response specifications.