System 1, the experiential one, is effortless, automatic, fast, opaque (we do not know that we are using it), parallel-processed, and can lend itself to errors. It is what we call “intuition,” and performs these quick acts of prowess that became popular under the name blink, after the title of Malcolm Gladwell’s bestselling book. System 1 is highly emotional, precisely because it is quick. It produces shortcuts, called “heuristics,” that allow us to function rapidly and effectively. Dan Goldstein calls these heuristics “fast and frugal.” Others prefer to call them “quick and dirty.” Now, these shortcuts are certainly virtuous, since they are rapid, but, at times, they can lead us into some severe mistakes. This main idea generated an entire school of research called the heuristics and biases approach (heuristics corresponds to the study of shortcuts, biases stand for mistakes).

Taleb, Nassim. The Black Swan (p. 81). Penguin Books Ltd. Kindle Edition.