By four in the afternoon, many business leaders have already made hundreds of decisions. Most of them were small. A few were not. And the quality of the last ones often looks nothing like the quality of the first.

That gap has a name in everyday conversation: decision fatigue. Lately, a growing number of leaders are trying to measure it in order to manage it with more awareness. Some are watching their sleep and recovery data. Others are tracking how many calls they take before noon. The interest in the topic of mental performance is real. But there are still a lot of open questions on the topic.

What Decision Fatigue Actually Is

The idea is simple. The more choices you make, the harder it gets to make the next one well. So people start to avoid making the decision today, go with the default option or decide on impulse.

It is worth being honest about the evidence. A widely cited study of parole judges, called the Hungry Judge Effect , suggested that favorable rulings dropped as a session went on and bounced back after breaks. That finding has been debated, and later research on the broader theory of willpower as a limited resource has had mixed results in replication.

The safest reading is this: whether there is a clean, measurable “decision battery” is still disputed, but mental effort, stress and poor rest clearly affect judgment.

What is not disputed is how it feels to the person having to make the decision. If you have ever agreed to something just to end a meeting, you know the pattern. For a practical look at the early signs, see how to spot decision fatigue before it costs you .

Why Leaders Want To Track Numbers For Performance

Leaders are used to measuring what matters. Revenue, pipeline, churn in a professional context. Sleep, heart rate, recovery time in their spare time. So far, mental performance has been the exception to this rule, because it felt too personal, too fuzzy or impossible to track.

Wearable devices could change this. They report sleep duration, resting heart rate and heart rate variability (HRV). These are real physiological signals. Lower HRV and a higher resting heart rate are generally associated with stress and incomplete recovery, and researchers use them in studies for exactly that reason.

If poor recovery shows up in the body, perhaps it can also warn you before your judgment slips.

What We Do Not Know Yet About Decision Fatigue

This is where caution matters. It is well established that stress and sleep loss affect the body and the quality of thinking. It is not established that a consumer wearable can tell you when you are about to make a bad decision. Those devices estimate recovery. They do not read your mind. Whether these signals can be turned into decision support for leaders is an open question.

The research that does give this idea a foundation is older and more careful. Neuroscientist Antonio Damasio’s somatic marker hypothesis proposes that the body produces fast physiological signals that influence choices before reasoning catches up. It is one reason people describe a gut feeling. It is also why paying attention to the body is not a strange idea. It is just a hard one to measure well. This is the same point explored in how to trust your gut without ignoring neuroschience.

Tracking Your Decision Fatigue Does Not Need A Device

You do not need a wearable to start. Many leaders get most of the value from a simple log. Once a day, write down three things: how well you slept, how many significant decisions you made before lunch and how confident you felt about the last one.

After two or three weeks, patterns tend to show up. Maybe your best strategic thinking happens before ten. Maybe Fridays are the worst day to approve anything big. Maybe back-to-back calls leave you with nothing left for the one that matters.

Design Your Day Around Your Mental Performance

Once you see your own rhythm, you can protect it. Put high-stakes decisions in your strongest window. Batch routine choices so they do not eat your best hours. Cut the number of small decisions with simple rules, like fixed meeting days or a default weekly menu.

Short breaks also help. A ten minute walk between heavy meetings is not a luxury. It gives your nervous system time to reset before the next round.