System 2 thinking has a limited budget of attention - you can only do so many cognitively difficult things at once.
This limitation is true when doing two tasks at the same time - if you’re navigating traffic on a busy highway, it becomes far harder to solve a multiplication problem.
This limitation is also true when one task comes after another - depleting System 2 resources earlier in the day can lower inhibitions later. For example, a hard day at work will make you more susceptible to impulsive buying from late-night infomercials. This is also known as “ego depletion,” or the idea that you have a limited pool of willpower or mental resources that can be depleted each day.
All forms of voluntary effort - cognitive, emotional, physical - seem to draw at least partly on a shared pool of mental energy.
The law of least effort states that “if there are several ways of achieving the same goal, people will eventually gravitate to the least demanding course of action.”
What makes some cognitive operations more demanding than others? Here are a few examples:
In the lab, the strain of a cognitive task can be measured by pupil size - the harder the task, the more the pupil dilates, in real time. Heart rate also increases.
Kahneman cites one particular task as the limit of what most people can do in the lab, dilating the pupil by 50% and increasing heart rate by 7bpm. The task is “Add-3”:
If you make the task any harder than this, most people give up. Mentally speaking, this is sprinting as hard as you can, whereas casual conversation is a leisurely stroll.
Because System 2 has limited resources, stressful situations make it harder to think clearly. Stressful situations may be caused by:
Because of the fixed capacity, you cannot will yourself to think harder in the moment and surpass the “Add-3” limit, even with a gun to your head. In the same way, you cannot sprint any faster than you can possibly sprint.
But there are some ways to make a mentally demanding task easier:
As we’ll find later, when System 2 is taxed, it has less firepower to question the conclusions of System 1.
Cognitive ease is an internal measure of how easy or strained your cognitive load is.
In a state of cognitive ease, you’re probably in a good mood, believe what you hear, trust your intuitions, feel the situation is familiar, are more creative, and are superficial in your thinking. System 1 is humming along, and System 2 accepts what System 1 says.
In a state of cognitive strain, you’re more vigilant and suspicious, feel less comfortable, invest more effort, and trigger System 2. You make fewer errors, but you’re also less intuitive and less creative.
Cognitive ease increases with certain inputs or characteristics of the task, including:
You don’t consciously know exactly what it is that makes it easy or strained. Rather, the ease of the task gets compressed into a single “is this easy” factor that then determines the level of mental strain you need to apply.
Drilling down into each input:
Exposing someone to an input repeatedly makes them like it more. Having a memory of a word, phrase, or idea makes it easier to see again.
Example experiments:
Even a single occurrence can make an idea familiar.
If the new idea fits your existing mental framework, you will digest it more easily.
Evolutionarily, this benefits the organism by saving cognitive load. If a stimulus has occurred in the past and hasn’t caused danger, later occurrences of that stimulus can be discarded. This saves cognitive energy for new surprising stimuli that might indicate danger.
However, this can cause a potentially dangerous bias. You will tend to like the ideas you are exposed to most often, regardless of the merit of those ideas.
You cannot easily distinguish familiarity from the truth. If you think an idea is true, is it only because it’s been repeated so often, or is it actually true? (Shortform note: thus, be aware of “common sense” intuitions that seem true merely because they’re repeated often, like “searing meat seals in the juices.”)
Furthermore, if you trust a source, you are more likely to believe what is said.
You can use the idea of cognitive ease to convince people to believe in the truth of something you’ve written. In general, to be more persuasive, make the message as easy to digest as possible. In other words, ease your listener’s cognitive load.
Consider the two statements:
Which one do you think is correct?
You likely found the first one a bit more believable, because it stood out. In reality, Hitler was born in 1889.
Here are tips to making your message more persuasive:
(Shortform note: In the O.J. Simpson trial, both mere exposure and clear display were used in catchphrases like “if the glove doesn’t fit, you must acquit.”)
In contrast, making cognition difficult actually activates System 2.
Cognitive ease is associated with good feelings. In contrast, cognitive strain tends to promote bad feelings.
The causality also works in the opposite direction: your emotional state affects your thinking.
Again, cognitive ease is a summary feeling that takes in multiple inputs and squishes them together to form a general impression. When you feel cognitively at ease, you’re not always aware oft why - it might be that the idea is actually sound and fits your correct view of the world, or that it’s simply printed with high contrast and has a nice rhyme.
Cognitive ease is associated with a “pleasant feeling of truth.” But things that seem intuitively true may actually be false on inspection.
Given that self-control and cognitive tasks draw from the same pool of energy, is there a relationship between self-control and intelligence?
Walter Mischel’s famous marshmallow experiment showed that children who better endured delayed gratification showed significantly better life outcomes, measured by SAT scores, education attainment, and body mass index.
Inversely, those who score lower on the Cognitive Reflection Test show more impulsive behavior, such as being more willing to pay for overnight delivery, or being less willing to wait for more time to receive more money. Poor scorers also show a greater tendency to fall prey to fallacies like the gambler’s fallacy (the assumption that if something occurs more frequently than usual now, it will happen less frequently than usual in the future) and sunk cost fallacy (discussed in Part 4-4).
As with most things in life, it appears that executive control has been attributed to both genetics and environment (parenting techniques).