Willpower tests mostly just measure how fast your eyes and muscles can move.
April 20, 2026
Original Paper
Non-decision time: the elephant in the executive control room
PsyArXiv · h369m_v1
AI-generated illustration
The Takeaway
Psychological research has relied on the stop-signal reaction time for decades to quantify inhibitory control and executive function. New analysis reveals that the majority of this score consists of low-level visuo-motor delays rather than actual brain power. Most of what researchers thought was a person's mental ability to cancel an action is just the physical speed of their peripheral nervous system. This means that thousands of studies on ADHD, addiction, and impulsivity might have mistaken slow reflexes for a lack of self-control. True willpower might be much harder to measure than anyone previously suspected.
From the abstract
Response inhibition is seen as a key facet of executive control, investigated in thousands of studies across psychology, psychiatry and neuroscience. It is most frequently studied using the stop-task, and its main outcome measure, the stop-signal reaction time (SSRT), is overwhelmingly interpreted as indicating top-down inhibitory ability or speed. Here we provide converging evidence that undermines this central assumption, from reanalyses of archival datasets and a novel preregistered study. We