6 Thinking fast and slow
In his book Thinking, Fast and Slow, Daniel Kahneman (2011) argues the case for two types of thinking.
‘System 1’ is fast, instinctive, often unconscious, and requires comparatively little effort. However, it tends to take shortcuts. System 1 is a necessary survival mechanism because staying alive requires making a continuous series of rapid decisions. But, at the same time, it is illogical and risks reaching conclusions that are mistaken.
‘System 2’, on the other hand, is slower and more considered, reasons much more logically, involves conscious thought, and generally takes a lot more effort.
As an example of fast and slow thinking, consider the following question.
Which weighs the most: a kilogram of lead or a kilogram of feathers?
At first, most people hear System 1 screaming, ‘Lead’s heavy, lead’s heavy!’
But then System 2 gets to work, pointing out that they are being fooled. A kilogram of anything weighs just that: a kilogram.
This example demonstrates a crucial fact about System 1 versus System 2 thinking. Often a question that requires System 2 thought (‘What does weigh a kilogram mean?’) gets replaced by a System 1 question (‘What’s heavy – lead or feathers?’) because the latter takes less effort to process.
Kahneman (2011) calls the question you are asked the target question (p. 97) and the simpler question it is replaced by the heuristic question (p. 129). The word heuristic originally meant a way of discovering things but is used by Kahneman to mean something like ‘quick and instinctive’.
One kind of heuristic question is availability. When people are asked to estimate how common something is, they substitute a simpler question: how readily do examples of it spring to mind? But this availability is very influenced by a range of factors other than the actual frequency. For example, something will have higher availability if it :
- is dramatic or frightening
- has recently been in the news
- is frequently reported in the news
- is familiar to you from personal experience.
The reason why the proportion of the population who are 65 or over is overestimated is probably a combination of factors 3 and 4.
The Fermi problem approach, on the other hand, is clearly in System 2 territory. Even though data sometimes has to be guessed, the overall process steers us towards more considered judgements.
Recalling the ‘super-forecasters’, these are people probably using System 2 thinking to make their predictions, rather than relying on hunches or intuition.
In Session 5 you will meet other examples of System 1 heuristics and the biases they introduce, and learn how thinking tools may equip you to avoid these dangers.