Thinking fast and slow: the two thought systems

Have you ever wondered how we make our decisions? Sometimes we seem to act very easily, as if we were on autopilot mode. Other times, we need to think hard before we decide what to do. The secret lies in the way our brain thinks. In his book “Thinking, Fast and Slow,” Daniel Kahneman explores this concept and explains to us how our brains make up their minds. It all boils down to two systems of thinking that he calls “System 1” and “System 2”.

System 1: Fast thinking

In order to understand system 1, let’s start with a small test. Look at the image below:

Angry woman

All it takes is a single glance to see the woman’s anger. As soon as you see the picture, you somehow “know” that she’s angry. You didn’t need to think about it, and you surely weren’t planning on assessing her mood. It just happened, in a moment of fast thinking.

This is exactly how system 1 works. It’s instantaneous, driven by instinct and prior learning. The accumulation of experiences in your life lead you to construct a profile of what an angry person looks like. You also know that anger can sometimes be dangerous to you, which is exactly why your brain signaled it as soon as you saw the picture.

In general, system 1 is the default option for information processing. The amount of information we collect every second (through vision, hearing, touch…) is enormous. If we had to consciously analyze every single bit of information all the time, we’d probably never do anything else in our life. That’s why system 1 does this work for us and alerts us when needed.

In addition to that, system 1 usually takes control when performing repetitive tasks. Any environment that doesn’t require complex thinking is a good candidate for system 1.

Characteristics of system 1

  • Fast
  • Automatic
  • Emotional
  • Intuitive
  • Practical
  • Error prone

System 2: Slow thinking

Just like we did with system 1, let’s start with a challenge:

25 * 16 = ?

Here’s what system 1 told you so far: this is a multiplication problem, and you can probably solve it using a pen and paper (or even mentally). You can also quickly know in what range the answer will be. However, you still don’t know the exact answer. The precise solution doesn’t intuitively come to your mind. You’ll need to focus, remember the multiplication table and the steps for performing a multiplication, then spend some time calculating the result. This is system 2.

System 2 is slower, driven by deliberation and logic. It’s not always on, but you can put it in use whenever the situation involves complex decisions or needs deeper analysis and thinking.

Characteristics of system 2

  • Slow
  • Logical
  • Deductive
  • Structured
  • Conscious
  • Reliable

Thinking: fast and slow

Thinking involves the use of both systems. And even though system 2 might seem like the hero, it’s system 1 that drives most of our thinking. Because of its automatic and fast nature, system 1 can sometimes jump to conclusions that affect our logical thinking. It’s the source of a lot of biases that we’ll talk about in detail in other articles.

Knowing these two modes of thinking can explain to us a lot of situations in our lives, and actually helps us become better decision makers. If you’re interested in knowing more about this, we suggest you listen to Kahneman himself talking about it:


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