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Latticework of Mental Models: Decision Fatigue

In January 2016, after two months of paternity leave when Mark Zuckerberg returned to work he asked his followers, showing off a picture of his wardrobe, for a suggestion about what he should be wearing to office. This is how his wardrobe looked.

Pretty drab collection, isn’t it? Zuckerberg has been wearing the same outfit, a grey t-shirt, for many years. The reminds us of Steve Jobs and his favourite black turtleneck.

So why do these billionaires who could afford almost anything in this planet, choose to stick to a simple attire?

The answer is – it’s their hack to simplify life.

According to Zuckerberg, making clothing decisions each day was a “frivolous” waste of time. I really want to clear my life, says Zuck, “to make it so that I have to make as few decisions as possible about anything except how best to serve this community.”

According to one estimate, we normally make somewhere around 35,000 decisions every single day. Many of those decisions are unconscious like walking, blinking, breathing and don’t need any extra mental effort. But the sheer volume of even those decisions that require at least some brain power like what to wear, where to eat, how to get to work, who to call when you get there, is staggering.

By the time you arrive at work, you’ve already made more decisions than most of our ancestors would make in a day. It’s pretty obvious that we make more decisions now than at any point in history.

Every time you have to make a conscious call to make a decision it consumes some mental energy and a bit of willpower. They problem with willpower is that it’s like a battery that runs out after a while. A prepaid card, if you will, which has a limited validity and limited usage.

The limited willpower theory explains why most diet and exercise plans don’t work. Scott Adams, creator of the famous cartoon strip Dilbert, writes in his book

Science has demonstrated that humans have a limited supply of willpower. If you use up your supply resisting one temptation, it limits your ability to resist others.

That explains how someone can resist junk all day but finally given in to a pack of cookies right before sleep. Resisting a temptation drains the willpower.

Decisions Deplete Willpower

Making decisions not only depletes willpower it erodes the physical stamina, reduces persistence, and even fuels procrastination.

In other words, after a spending a demanding day making a string of decisions the decision-muscle wears out. This is called Decision Fatigue. In case of physical fatigue, you at least notice the tiredness. Unfortunately, mental fatigue doesn’t come with such clear cues. A fatigued brain is usually unaware that it’s running low on mental energy i.e., there’s no telltale symptom of when that willpower is low.

The more the options available to choose from bigger the blow to the willpower store. Like a deer caught in a flashlight, the human brain paralyses when it’s bombarded with too much information. Barry Schwartz has written about this concept in great length in his book, The Paradox of Choice.

Decision fatigue makes us more prone to lose our temper while dealing with family and friends, binge on fatty and sugary food, and splurge money on the latest gizmo available in online flash sale. Put simply, decision fatigue leads to irrational behaviour resulting in uncontrollable impulses to eat, drink, spend and say stupid things.

Daniel Kahneman, a Nobel laureate and author of Thinking Fast and Slow, writes –

Several psychological studies have shown that people who are simultaneously challenged by a demanding cognitive task and by a temptation are more likely to yield to the temptation. Imagine that you are asked to retain a list of seven digits for a minute or two. You are told that remembering the digits is your top priority. While your attention is focused on the digits, you are offered a choice between two desserts: a sinful chocolate cake and a virtuous fruit salad. The evidence suggests that you would be more likely to select the tempting chocolate cake when your mind is loaded with digits.

Decision fatigue can have very serious implications especially in areas like judicial process. Here’s an example from the book Art of Thinking Clearly

Four prisoners in an Israeli jail petitioned the court for early release. Case 1 (scheduled for 8.50 a.m.): An Arab sentenced for 30 months for fraud. Case 2 (scheduled for 1.27 p.m.): A Jew sentenced to 16 months for assault. Case 3 (scheduled for 3.10 p.m.): A Jew sentenced to 16 months for assault. Case 4 (scheduled for 4.35 p.m.): An Arab sentenced for 30 months for fraud. How did the judge decide?

More significant than the detainee’s allegiance or the severity of their crimes was the judge’s decision fatigue. The judges granted request 1 and 2. However, they struck out applications 3 and 4 because they could not summon enough energy to risk the consequences of an early release…A study of hundreds of verdicts shows that within a session, the percentage of courageous judicial decisions gradually drops from 65% to almost zero.

Which means when the judges feel mentally drained, they don’t want to take chances and usually prefer to stick to status quo. Taking a cue from this example, Dobelli suggests that if you ever have an option of presenting a promising idea to your boss, take the morning slot.

Decision Diet

There is no direct way to deal with decision fatigue. You can’t fight it; you can’t undo it. The only way to replenish the willpower quota is to take a good night’s sleep. Although refuelling (food) can also reverse the decision fatigue to some extent but stuffing yourself with calories, just to keep willpower up, isn’t really a bright idea.

So the simplest solution is to reduce the number of decisions you make. Automating many of those decisions which require conscious effort is a great way to cut down on the number of decisions. Habit formation, thus, becomes a very useful tool. Habits don’t require active participation of the conscious mind. A habit allows your brain to operate on a set routine, hence eliminating the need for low-level decision making.

You could start with very basic stuff like what to eat for breakfast, what to wear every day, and when to go to bed. This will gradually cut down the decision fatigue.

How do you automate the problem of what to wear? Zuckerberg’s wardrobe is the simplest answer.

Now even if you automate many of your basic decisions you may still be left with a handful of unexpected activities presenting themselves during the day which require you to flex your decision muscle.

If you continue to make decisions under the spell of decision fatigue, the quality of your decisions will go down rapidly. Chronic mental fatigue leads to early burnout at work, loss of motivation, poor concentration, and hampers the brain’s ability to effectively process the information.

So to ensure that your limited stock of willpower is utilized for important decisions is to make those critical decisions earlier in the day, which means addressing the critical tasks before getting on to trivial stuff. It’s a great way to beat decision fatigue by saving small decisions for after work (when decision fatigue is greatest) and to tackle complex decisions in the morning when your mind is fresh. You don’t want your important decisions to be lined up for the later part of the day after you have squandered the limited quota of willpower on relatively unimportant decisions. Truly wise businessmen avoid restructuring their company at 5 p.m.

Decision fatigue is found in all sorts of different professions and activities. One Harvard Business Review article claims –

Evidence for the same type of cognitive fatigue has been found in other contexts, including consumers choosing among various products and physicians prescribing antibiotics. Primary care doctors often prescribe unnecessary antibiotics for acute respiratory infections (ARI), researchers have found. As the physicians appeared to “wear down” during their morning and afternoon clinic sessions, the rates at which they prescribed antibiotics increased. About 5% more patients receive antibiotics at the end of a clinic session as compared to the beginning, this research shows. Thus, while clinicians make many patient care decisions each day, the cumulative demand of these decisions leads to more inappropriate choices later in the day.

When Barack Obama was the president of United States, supposedly the most powerful person on earth and perhaps the busiest too, said this –

You’ll see I wear only grey or blue suits. I’m trying to pare down decisions. I don’t want to make decisions about what I’m eating or wearing because I have too many other decisions to make.

Social psychologist Roy F. Baumeister has done extensive study on the subject of decision fatigue. “Good decision making is not a trait of the person, in the sense that it’s always there,” Baumeister says. “It’s a state that fluctuates.”

Roy’s research shows that people with the best self-control are the ones who design their lives to conserve willpower. They don’t schedule endless back-to-back meetings. They understand that going for all-you-can-eat buffets for lunch is a big drain on store of willpower. Instead of deciding every morning whether or not to force themselves to exercise, they set up regular appointments to work out and simply show up. Instead of relying on willpower to remain strong all day, they consciously conserve it so that it’s available for emergencies and during those unexpected moments requiring unplanned important decisions.

In Investing

When it comes to making decisions in investing, noted value investor Guy Spier writes –

I actually think it’s quite possible that my returns would not be much worse and might even be better if I was only allowed to trade on one day a year, so every January 1st or the first week in January, make all my trades and then not do anything for another year and just let those decisions build up.

Charlie Munger says –

The way to win is to work, work, work, work and hope to have a few insights.

Now, the question is – how many insights do you need in your investing lifetime?

Not many, as Munger says –

…you don’t need many in a lifetime. If you look at Berkshire Hathaway and all of its accumulated billions, the top ten insights account for most of it. And that’s with a very brilliant man—Warren’s a lot more able than I am and very disciplined—devoting his lifetime to it. I don’t mean to say that he’s only had ten insights. I’m just saying, that most of the money came from ten insights.

So you can get very remarkable investment results if you think more like a winning pari-mutuel player. Just think of it as a heavy odds against game full of craziness with an occasional mispriced something or other. And you’re probably not going to be smart enough to find thousands in a lifetime. And when you get a few, you really load up. It’s just that simple.

Warren Buffett is supposed to have said this at a business school –

I could improve your ultimate financial welfare by giving you a ticket with only twenty slots in it so that you had twenty punches – representing all the investments that you got to make in a lifetime.

And once you’d punched through the card, you couldn’t make any more investments at all. Under those rules, you’d really think carefully about what you did, and you’d be forced to load up on what you’d really thought about. So you’d do so much better.

The problem with most of us investors is that, too often, we sprinkle money around while telling ourselves, “Okay, let me throw a little money in this stock and little in that stock and then see what happens. At least, one of the stocks will work!”

Now, that’s a sure shot road to a hell lot of risk – first you don’t know where you are scattering your money, and then you think you are investing while the reality is that you are speculating in the hope of hitting the “right” stock.

Buffett wrote this in his 1993 letter to shareholders…

Charlie and I decided long ago that in an investment lifetime it’s just too hard to make hundreds of smart decisions. That judgment became ever more compelling as Berkshire’s capital mushroomed and the universe of investments that could significantly affect our results shrank dramatically.

Therefore, we adopted a strategy that required our being smart – and not too smart at that – only a very few times. Indeed, we’ll now settle for one good idea a year. (Charlie says it’s my turn.)

Munger adds…

To me, it’s obvious that the winner has to bet very selectively. It’s been obvious to me since very early in life. I don’t know why it’s not obvious to very many other people.

Now, making fewer decisions doesn’t mean reading fewer books or analysing fewer businesses. Please don’t confuse between decision and activity. In fact, making fewer decisions gives you more space for increasing your activities.


Too many choices can be overwhelming to your brain, so it’s best to make some cuts to allow for more focused thinking.

Whether it’s Steve Jobs’ famous black turtleneck or Mark Zuckerberg’s grey t-shirt and hoodie, they are all simple results of daily routines intended to cut down on decision fatigue.

But if it seems too weird to stick to a monochromatic attire, you might consider laying out your outfit at night so you don’t even have to think about it when you wake up.

The learned man aims for more, goes the adage, but the wise man decreases and then decreases again.

The best decision makers know when not to trust their willpower.

Decide less, decide better.

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About the Author

Anshul Khare worked for 12+ years as a Software Architect. He is an avid learner and enjoys reading about human behaviour and multidisciplinary thinking. You can connect with Anshul on Twitter.


  1. It’s amazing how something as iconic as Zuck, Jobs and Obama wearing the same clothes repeatedly is actually linked to better decision making, Anshul.

    I’ve felt decision fatigue (and crankiness) many times, and have felt better when I ate something. In Thinking Fast and Slow itself, Kahneman highlights how infusion of glucose in the body leads to a rise in mood and decision making abilities. As you rightly said, we cannot keep adding calories to our body. But we probably can reduce the food we intake during regular times to consume healthy food at such times.

    Exercise is also another powerful way. The fittest athletes are also the most resilient and the fastest decision-makers.

    Superb post as always!

  2. kundavar says:

    Superb one! Take a bow Vishal!


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