Differential contributions of inhibition and task engagement to workload: Evidence from a novel adaptive Stroop task

This study examined the effects of inhibitory load and task engagement on workload through self-report, behavioral, and physiological measures. Thirty-five adults completed Stroop task versions designed to manipulate inhibitory load—by varying Stroop congruency—and task engagement—through adaptive and non-adaptive pacing. Greater inhibitory load (vs. lower load) induced greater perceived workload along with impaired performance, increased visual engagement, and reduced boredom. Greater task engagement (vs. lower engagement) induced an even greater perceived workload, along with more efficient information processing, increased visual engagement (reduced blinking), and small reduction in parasympathetic tone from baseline (reduced heart rate variability). It also led to increased and anticipated perceived mental fatigue, while mitigating the increases in sleepiness observed under lower engagement. These findings demonstrate that perceived workload is sensitive to inhibitory load and task engagement. Combining high inhibitory load and adaptive pacing produced the greatest perceived workload, offering a promising paradigm for advancing workload research.