Our Two Brains, Mindfulness and Decision Making
Long before any of the neuroscience was known, Winston Churchill said “fear is a reaction. Courage is a decision”[i]. Although he didn’t know it, Mr. Churchill was describing two separate yet conjoined systems operating in our heads. Over the past 15 years the function and anatomy of these systems has been described in both scientific and general publications. Two of the more popular descriptions of these systems and how they operate are the Default Mode Network (DMN) and Nobel prize recipient Daniel Kahneman’s System 1 / System 2 detailed in his widely acclaimed book Thinking, Fast and Slow[ii]. On a macro level, the DMN and Kahneman’s System 1 share the same functionality and are also consistent, along with Kahneman’s System 2, with work described by addiction psychiatrist and neuroscientist Judson Brewer[iii]. Together, they help inform our understanding of mindfulness and how the decision-making process works.
The DMN was first described as such in the early 2000’s by Raichle and colleagues at Washington University in St. Louis[iv]. It was discovered while researchers were looking to measure baseline brain activity and, instead of finding an electrically “quiet” brain, they saw that people at “rest” had lots of consistent brain activity, especially in two areas known as the medial prefrontal cortex (mPFC) and the posterior cingulate cortex (PCC)[v] (Figure 1). In short, this early work and subsequent investigations showed that at rest, we are actually thinking a lot, essentially daydreaming, and these brain regions are active. One of the common components of our “thoughts” in this state is that they are self-referential. In other words, we are thinking about ourselves in some way — for example, fantasizing about what we will do in the future or what so-and-so did to us in the past. In fact, it turns out that we spend about 50% of our waking hours in this state[vi].
Separately, Kahneman famously described System 1 and System 2, the fast and slow systems respectively. System 1 is an evolutionarily old and primitive emotional system. It resides in areas including the mPFC and the PCCii which, not coincidently, is the same as the DMN. System 1 bypasses rational thought, is largely subconscious and is very fast. Its speed is both its greatest attribute and downside. For example, when one is physically threatened, System 1 is the go-to network, invoking the commonly referred to fight-or-flight response. As we have evolved however, life situations have become more nuanced and such binary decisions are not as useful, but our basic neuroanatomy hasn’t yet entirely caught up to this. Instead we continue to, by default, operate in System 1 most of the time. In fact, the more stressed we are the more this is the case. While this may still convey some survival advantage, it is certainly not optimized for modern living. For example, despite what your old brain is whispering to you when you are having a disagreement with your spouse or co-worker, fight or flight are clearly not the two most functional options. They, on their own, will likely not lead to a great outcome.
Kahneman’s System 2 on the other hand, involves the evolutionarily more recent dorsolateral PFC (dlPFC)iii. System 2 is slower and credited with more thoughtful and conscious decisions. This is consistent with the notion that early brain regions were built to be reactive and fast as that is what was needed at the time. Later brain regions evolved because our needs changed as we changed or, alternatively, our needs changed as our brain evolved. Either way, the ability for us to reason and override instinct arrived only relatively recently.
So, getting back to the title of this article, how do these brain systems relate to mindfulness and decision making. It turns out that mindfulness practice impacts the same brain regions described above[vii]. This of course makes sense. One key part of the definition of mindfulness is being present in, or aware of, the current moment; the opposite of being caught up in daydreaming. Think DMN. The other definitional component is being non-judgmental. This one requires some explanation. When, for example, judging something as good or bad, the judgment is relative to us personally. I don’t like blue couches. That person’s voice really bugs me. I love scrambled eggs. All of these “judgments” are self-referential. Remember the self-referential role of the PCC in the DMN.
In mindfulness training one learns to be present (not daydreaming) in whatever is happening at that moment and, importantly, in a non-judgmental way. In other words, one learns to allow themselves to be well connected to, and actually part of, objective reality. Mindfulness then describes a state of mind where System 2 is available, the DMN (System 1) is not dominating and self-referential thinking is minimized. In other words, one is fully engaged, aware of others, not thinking excessively about themselves and accepting reality as it is at that moment. It’s a state where one can decide, as Mr. Churchill suggests, to be courageous.
[i] Widely attributed but not always to Winston Churchill
[ii] Kahneman, D. (2011). Thinking, fast and slow. New York, NY, US: Farrar, Straus and Giroux.
[iii] Brewer, J. (2018). The Craving Mind: From Cigarettes to Smartphones to Love? Why We Get Hooked and How We
Can Break Bad Habits: Yale University Press
[iv] https://en.wikipedia.org/wiki/Default_mode_network
[v] Christopher G. Davey,Jesus Pujol,Ben J. Harrison. Mapping the self in the brain’s default mode network
NeuroImage, Elsevier, 15 May 2016
[vi] Brewer J. A., Worhunsky P. D., Gray J. R., Tang Y.-Y., Weber J., Kober H. (2011). Meditation experience is associated with differences in default mode network activity and connectivity. Proc. Natl. Acad. Sci. U.S.A. 108, 20254–20259. 10.1073/pnas.1112029108
[vii] Garrison KA, Zeffiro TA, Scheinost D, et al. Meditation leads to reduced default mode network activity beyond an active task. Cogn Affect Behav Neurosci. 2015;15:712–720.