The curve of control: Nonmonotonic effects of task difficulty on cognitive control

The U-shaped curve has long been recognized as a fundamental concept in psychological science, particularly in theories about motivational accounts and cognitive control. In this study (N = 330), we empirically tested the prediction of a nonmonotonic, curvilinear relationship between task difficulty and control adaptation. Drawing from motivational intensity theory and the expected value of control framework, we hypothesized that control intensity would increase with task difficulty until a maximum tolerable level, after which it would decrease. To examine this hypothesis, we conducted two experiments utilizing Stroop-like conflict tasks, systematically manipulating the number of distractors to vary task difficulty. We assessed control adaptation and measured subjective task difficulty. Our results revealed a curvilinear pattern between perceived task difficulty and adaptation of control. The findings provide empirical support for the theoretical accounts of motivational intensity theory and expected value of control, highlighting the nonlinear nature of the relationship between task difficulty and cognitive control.