Book Cover


This week we re-read Chapter 3 of Thinking, Fast and Slow by Daniel Kahneman. One of the core themes in this chapter is the concept of ego depletion.  Ego depletion is a theory that self-control, as a form of system 2 thinking, draws from a finite pool of mental resources. When the pool is low, so is self-control. I did some research on the topic and the evidence is mixed whether there is an ego depletion impact. Regardless, from the point of view of Chapter 3 the idea is that heavy mental and physical loads on a person spread their ability to think and make decisions thin is not a stretch (and we should not expend a significant cognitive load on the topic). Whether the triggering mechanism is ego depletion or something else is not as important as the observable impact – when people are under mental stress they don’t always make the most thoughtful decisions.   

System 2 thinking is always active. System 2 thinking monitors your daily interactions and activity which are handled by System 1 thinking. I like the analogy of a virtual assistant like Alexa, it’s always listening, burning a minimal amount of power until it hears a trigger, then the level of processing jumps exponentially.  System 2’s monitoring is part of the cognitive load on the brain, just like the system monitor on your PC or laptop. When System 2 swings into action it uses more resources. For example, reading and processing email requires System 2 thinking. The additional processing requirements are drawn from System 1 thinking activities such as breathing. This redistribution of cognitive load from System 1 to System 2 is one possible cause of  Email Apnea (yes that is a real thing).  

Extremes cause competition for resources which causes the brain to switch between tasks.  Kahneman suggests that frequent switching between thinking processes is not intrinsically pleasurable which is why the brain seeks to avoid switching when possible.  Kahneman invokes Deepak Chopra’s law of least effort(principle of least action or resistance) as he is explaining why System 2 is lazy. As an illustration, Kahneman explores the idea of flow.  Flow is a state where you are able to focus attention and concentration on a hard problem or intellectually stimulating task (like writing, coding or testing) while blocking out anything that would challenge your self-control. In a flow state, you are not expending energy on self-control, therefore, freeing resources to do slow thinking.

Midway through the chapter, Kahneman turns to the impact of cognitive load on self-control.  He cites research that shows that people are more susceptible to temptation when they are exerting significant mental effort.  When people under significant cognitive load they more apt to fall prey to the biases intrinsic in System 1 thinking which causes a loss of self-control.  That bag of microwave popcorn I ate on Thursday night while reading this chapter might be a direct reflection of this type of thinking. This is a form of ego depletion.  

Ego depletion occurs faster when the physical system is under stress. For example, Kahneman tells the story of parole judges whose highest parole rates are just after eating and lowest just before (perhaps they should have a Snickers bar before every case). As the body’s energy reserve is run down the amount of energy left to divide between system 1 and 2 thinking gets smaller.  

Because System 2 is lazy (Kahneman’s word) it does not always kick in unless a person steps back and slows down the thought process. Unless a person slows down and invokes System 2 thinking, System 1 thinking might generate the wrong answer. Kahneman uses a set of puzzles (page 44) to show how quick thinking will generate a plausible albeit the wrong answer.  In the examples, if someone slows down and expends the effort to use System 2 thinking the right answer could be arrived at. System 2 is lazy because System 1 generates an answer quickly and easily – providing immediate gratification. But because System 1 is biased, the answer can be wrong.

If you do not have a favorite, dog-eared copy of Thinking, Fast and Slow, please buy a copy.  Using the links in this blog entry helps support the blog and its alter-ego, The Software Process and Measurement Cast. Buy a copy on Amazon,  It’s time to get reading!  

The previous installments:

Week 1: Logistics and Introduction

Week 2: The Characters Of The Story

Week 3: Attention and Effort