Perseverative behavior and adaptive control in older adults: performance monitoring, rule induction, and set shifting.

Older adults, like patients with dorsolateral frontal lobe lesions, have been shown to be progressively susceptible to errors of perseveration in the Wisconsin Card Sorting Test (WCST). This deficit may result from several types of endogenous adaptive control abilities. First, to enable behavioral modifications in response to sudden changes in task demands, one has to consider and evaluate the possible alternative categorization rules and select one for further testing (rule induction). Second, to perform the required shift appropriately, one should suppress the no-longer relevant task set and replace it by an appropriate new one (set shifting). Third, however, proper application of rule-induction and set-shifting abilities requires the ability to monitor and interpret task cues and feedback signals appropriately to guide behavior and to recognize the need to apply rule-shift operations (performance monitoring). To explore the extent to which these different endogenous adaptive control abilities are differentially sensitive to the effect of aging, young and older adults were tested in two experiments using WCST-like tasks. From the finding that older adults were not able to capitalize on explicit shift cues (either nonspecific or specific) the inference can be drawn that basic set-shifting abilities, rather than rule-induction or performance-monitoring abilities, were the primary factor responsible for the increased tendency to perseverate as adults grow into senescence.