To survive physically or psychologically, we sometimes need to react automatically to a speeding taxi as we step off the curb or to the subtle facial cues of an angry boss. That automatic mode of thinking, not under voluntary control, contrasts with the need to slow down and deliberately fiddle with pencil and paper when working through an algebra problem. These two systems that the brain uses to process information are the focus of Nobelist Daniel Kahneman's new book, Thinking, Fast and Slow (Farrar, Straus and Giroux, LLC., 2011). The following excerpt is the first chapter, entitled "The Characters of the Story," which introduces readers to these systems. (Used with permission.)
Understanding fast and slow thinking could help us find more rational solutions to problems that we as a society face. For example, a commentary in the March issue of the journal Nature Climate Change outlined how carbon labeling that appeals to both systems could be more successful than previous efforts to change consumer habits. (Scientific American is part of Nature Publishing Group.) Understanding how we think can also guide more personal decisions. Last month, Kahneman highlighted in a lecture given at the National Academy of Sciences "The Science of Science Communication" conference how realizing the limitations of each system can help us catch our own mistakes.
To observe your mind in automatic mode, glance at the image below.
Your experience as you look at the woman’s face seamlessly combines what we normally call seeing and intuitive thinking. As surely and quickly as you saw that the young woman’s hair is dark, you knew she is angry. Furthermore, what you saw extended into the future. You sensed that this woman is about to say some very unkind words, probably in a loud and strident voice. A premonition of what she was going to do next came to mind automatically and effortlessly. You did not intend to assess her mood or to anticipate what she might do, and your reaction to the picture did not have the feel of something you did. It just happened to you. It was an instance of fast thinking.
Now look at the following problem:
17 × 24
You knew immediately that this is a multiplication problem, and probably knew that you could solve it, with paper and pencil, if not without. You also had some vague intuitive knowledge of the range of possible results. You would be quick to recognize that both 12,609 and 123 are implausible. Without spending some time on the problem, however, you would not be certain that the answer is not 568. A precise solution did not come to mind, and you felt that you could choose whether or not to engage in the computation. If you have not done so yet, you should attempt the multiplication problem now, completing at least part of it.
You experienced slow thinking as you proceeded through a sequence of steps. You first retrieved from memory the cognitive program for multiplication that you learned in school, then you implemented it. Carrying out the computation was a strain. You felt the burden of holding much material in memory, as you needed to keep track of where you were and of where you were going, while holding on to the intermediate result. The process was mental work: deliberate, effortful, and orderly—a prototype of slow thinking. The computation was not only an event in your mind; your body was also involved. Your muscles tensed up, your blood pressure rose, and your heart rate increased. Someone looking closely at your eyes while you tackled this problem would have seen your pupils dilate. Your pupils contracted back to normal size as soon as you ended your work—when you found the answer (which is 408, by the way) or when you gave up.