Cognitive stamina is your cognitive budget, so to speak. It represents your ability to do intellectual work throughout the day.

Cognitive stamina is generally believed to be a resource that gets depleted with time. Think of it as a muscle: the more you use it, the more it gets exhausted. So every single decision, big or small, digs into your cognitive stamina bank account.

So what happens when you run out of cognitive stamina? You go back to actions which are routine and don’t require a lot of thought from you. That’s partly why after a long day at work you are more likely to skip the gym and reach for that triple chocolate cake. You go back to your lazy self, until your stamina recharges completely overnight, or gets a partial refill after a meal or sugary snack.

Willpower - is it a finite resource?

In everyday life, we call this willpower. But scientists are more likely to talk about decision fatigue or ego depletion. That’s thanks to Roy F. Baumeister, who revived an old Freudian hypothesis.

Initially, Freud theorized that mental activities involved the transfer of energy. The self, or ego, depended on these mental activities. But Freud was quite vague in the details, and his energy model of the self was ignored until Baumeister started looking closer at the field of mental discipline.

Through a series of experiments, Baumeister showed that there is a finite source of mental energy that allows us to use self-control. For example, when subjects forced themselves to not cry during a sob-story movie, they gave up more quickly on subsequent lab tasks requiring self-discipline (like working on geometry puzzles or squeezing a hand-grip exerciser). Similarly, when people resisted the temptation of freshly baked chocolate-chip cookies or M&Ms, they were less able to resist other temptations later on.

How about decision making?

The examples above paint an interesting picture of how willpower might be a finite resource. But how does decision making play into this? And more importantly, does it dig into your cognitive stamina resources?

Even though Baumeister’s work on willpower is seminal, it wasn’t until Joan Twenge, a postdoctoral fellow, started working at Baumeister’s lab that we got the first glimpse of how decision making saps cognitive stamina.

As she studied the results of the ego-depletion experiments, Twenge remembered how exhausted she felt on a particular night after she and her fiancé had registered for wedding gifts. She shared this insight with he colleagues, who also recognized these symptoms in themselves after making decisions. So they designed a new experiment.

Researchers went off to fill their car trunks with products from a nearby department store that was holding a going-out-of business sale. When the subjects - college students - came into the lab, they were told they could keep an item at the end of the experiment, but had to make a series of choices first.

Would they prefer a pen or a candle? A vanilla-scented candle or an almond-scented one? A candle or a T-shirt? A black T-shirt or a red T-shirt?

In the meanwhile, the control group spent the same amount of time contemplating all these products, without having to make choices. They were then asked to report their opinion of each product and report how often they had used a product like that during the previous six months.

Then, all subjects were given a classic self-control test - holding your hand in ice water for as long as you can. Of course, the impulse is to pull out your hand, so self-discipline is required if you are to keep your hand underwater for as long as possible.

As it turns out, the students who had to make decisions in the beginning of the experiment gave up much faster. They only lasted 28 seconds, while the control group lasted 67 seconds on average. Apparently, making all those choices drained the students’ self-control! (The results were later confirmed in other experiments that tested students after they chose their courses from the college catalog, for example.)

So how do you improve your cognitive stamina?

There are always little things you can do to manage and improve your cognitive stamina. Here are just a few of them:

1. Reduce the number of decisions you make in a day

This seems a given, after reading the results of Twenge’s and her team’s experiments. The less choices you have, the more cognitive stamina you have to apply to other areas of your life.

Think about the things that are important to you - truly important, like your business, your health, your family. Would you want them to get anything less than they deserve at the expense of trivial decisions, like what shoes to wear today?

Try to find ways to diminish the number of decisions you make in a day. Things like what to wear and what to eat are probably the easiest to begin with. For example, Steve Jobs used to choose a black turtleneck from a pile of other black turtlenecks every morning - a task with a cognitive load of zero.

I’m not saying ditch your whole closet for black turtlenecks. But do try to habitualize as many of your daily routines as possible. Even trying to choose your clothes and prepare your meals the day before can allow you to start your day with more cognitive stamina, since those decisions are made by most of us in the morning.

2. Balance future-oriented tasks with present-oriented tasks

A theory based on evolutionary psychology has it that our choices are based on the expected utility over time. In other words, the higher your cognitive stamina, the more likely you are to perform a very future-oriented task (like, preparing for next week’s presentation). Simply, it’s more affordable.

Try to balance future-oriented tasks with present-oriented tasks. Things that your ‘survival’ depends on right now are easier to do right away, even when your cognitive stamina has been depleted. On the other hand, tasks that require more cognitive stamina and are not immediately rewarding, should be done when your cognitive stamina is at its highest - for most people, first thing in the morning.

3. Get better sleep

Sleeping is vital for the health of the prefrontal cortex - the area of the brain associated with decision making and self-control. Don’t underestimate a good night’s sleep!

In her book The Willpower Instinct, Kelly McGonigall writes:

"Sleep deprivation (even just getting less than six hours a night) is a kind of chronic stress that impairs how the body and brain use energy. The prefrontal cortex is especially hard hit and it loses control over the regions of the brain that create cravings and the stress response."

But when you’re strapped for time, even a quick nap can have restorative powers for your cognitive stamina.

The power of belief

Some studies have found that beliefs actually influence your cognitive stamina.

In a Psychology Today article, Robert Kurzban explains this with a colourful example: “If I’m out of gas but I think the tank is full, the car still won’t go.” Believing the tank is full won’t do a thing.

But studies show quite the opposite when it comes to cognitive stamina. This hints at the fact that cognitive stamina may not really be finite. In one study, for example, people who were told that the resource model - where cognitive stamina gets depleted - was false ended up doing better on tasks than those who believed it was real.

The truth is probably somewhere in the middle - there are surely biological limits to willpower. Food and sleep are just a couple of examples.

Of course, it’s easier to write off our failures to biological limits. But in the end it pays off a lot more to actually take ownership over our biological limits, and, why not, try to push them back a little bit.

Photo credit: shoobydooby, cc