No need to choose: independent regulation of cognitive stability and flexibility challenges the stability-flexibility tradeoff

Abstract

Adaptive behavior requires the ability to focus on a current task and protect it from distraction (cognitive stability) as well as the ability to rapidly switch to another task in light of changing circumstances (cognitive flexibility). Cognitive stability and flexibility have commonly been conceptualized as opposite endpoints on a stability-flexibility tradeoff continuum, implying an obligatory reciprocity between the two: greater flexibility necessitates less stability, and vice versa. Surprisingly, rigorous empirical tests of this critical assumption are lacking, however. Here, we tested this assumption by acquiring simultaneous measurements of cognitive stability (congruency effects) and flexibility (switch costs) while independently varying contextual demands on these functions with block-wise manipulations of the proportion of incongruent trials and task switches, respectively. If cognitive stability and flexibility are reciprocal, an increase in flexibility in response to higher switch rates should lead to a commensurate decrease in stability, and an increase in stability in response to more frequent incongruent trials should result in decreased flexibility. Across three experiments, using classic cued task switching (Experiments 1 and 3) and attentional set shifting (Experiment 2) protocols, we found robust evidence against an obligatory stability-flexibility tradeoff. Although we observed the expected contextual adaptation of stability and flexibility to changing demands, strategic adjustments in stability had no influence on flexibility, and vice versa. These results refute the long-held assumption of a stability-flexibility tradeoff, documenting instead that the cognitive processes mediating these functions can be regulated independently - it is possible to be both stable and flexible at the same time.