Tuesday, November 6, 2012

The Importance of Continuity in “Thinking Fast and Slow”

I thoroughly enjoyed Daniel Kahneman’s new book: “Thinking Fast and Slow.” I recommend it widely but I have some recommendations. If I wrote the book I would have presented the material a little differently. I think that the central dichotomy, that between “thinking fast” and “thinking slow” is interesting, but the commonalities between the two are perhaps more interesting. He describes thinking fast and slow as fundamentally different cognitive processes subserved by two distinct architectures, “system 1” and “system 2.” I think that the two use the same general brain architecture, and that thinking slow is actually thinking fast, turned in on itself. By this I mean that what he calls thinking slowly is just thinking fast about the last few fast thoughts that just took place. Thus thinking slowly is still impulsive and automatic, and uses the same neurophysiological processes, but it involves the sustained maintenance of certain representations through time. The maintenance of certain features throughout a series of fast thoughts creates the mental continuity that is the hallmark of slow thinking.

As Kahneman describes it, thinking fast involves judgments, perceptions or interpretations that are made very quickly, automatically and using expertise. Thinking slow involves more concerted, reflective thinking that takes more time, is algorithmic (in the sense that it involves sequential problem solving steps) and effortful. Again, I think that this dichotomy represents a valuable schema for thinking about the mind and I think his exploration of it in the book is valuable and meaningful. However…

I believe that thinking slowly happens when we have several fast thoughts that are all interrelated. Instead of jumping to a conclusion or judgment about something based on a single impulse, thinking slowly involves the sequential arrangement of several impulses that, progressively and cooperatively, lead to a single conclusion or judgment. When talking about slow thinking, Kahneman gives the example of multiplying two, two-digit numbers. This is a calculation that involves a series of impulses arranged in a specific way that follows a learned pattern of steps. According to Kahneman such a calculation is not supposed to involve fast thinking, but I think it involves fast thoughts that are coordinated together to implement algorithmic steps. Most importantly it involves a series of fast thoughts with shared or interrelated content rather than disparate content.

I think that thinking fast happens when several nodes in association areas are made active and then used to build top-down imagery. I think that thinking slow involves doing this several times sequentially, culminating in a judgment that could not be informed by any of the intermediate steps alone. In other words, memories created by fast thoughts inform subsequent fast thoughts leading to a slow progression of fast thinking that is capable of solving a problem too difficult for any one fast thought by itself.

To me all actions, judgments and cognitions fall on a continuum between very fast and very slow thinking. Fast thoughts are short, discrete, and have little continuity to them. Slow thoughts are longer, have more continuity, and are marked by the conservation of several representations across time. Thinking fast and slow exist together on a continuum, where fast thinking involves less PFC activity and slow thinking involves more. Kahneman says that slow thinking is initiated by motivation, surprise or curiosity. Of course motivation, surprise and curiosity are exactly the factors responsible for recruiting the dopamine necessary to allow the sustained PFC firing responsible for working memory and mental continuity in rodents and humans. 

Kahneman also says that thinking slow is a response to mental strain, stress or a difficult mental task. I would categorize “stressed thinking” as a third type of thinking that often accompanies thinking slow. I wouldn’t say that thinking in response to stress is slow thought, especially because prolonged acute stress and chronic stress actually increase the emphasis on procedural and implicit thinking. In fact, the inverted-U effect observed between stress and cognition shows that both fast and slow thinking are facilitated by stress but that if the stress persists slow thinking is compromised and hindered. Thus it seems that the effects of stress on slow thinking are variable and depend on how significant and long lasting the stressors are. Also the effects of stress may actually be orthogonal to the fast/slow continuum. This brings us to the importance of having more precise operational definitions for fast and slow thinking, and I think that this can be done once their neurobiological underpinnings and better understood.

Read the full article that I wrote on this topic here:




  1. This book is one of the best books I have read (not yet completed) about the functioning of the Brain!

    Daniel takes the reader on a fun filled journey filled with experiments to try out and facts that we never knew, but at same time explains about the functioning of our thought process, reactions and the reason why we do what we do!

    To sum it up... Buy it! Its informative as well as fun to read.

  2. This book will force you to reconsider what you have always thought about your thinking and how you make decisions. The decision whether or not to read this book is an easy one. Don't think about it. Do it now.