Whether you practice nondirective meditation like Acem, mindfulness meditation, or some other type of meditation, you will experience intermittent mind wandering during your practice.
Some techniques aim to reduce this spontaneous stream of thoughts, while nondirective meditation types integrate them as an important part of meditation. But where in the brain do these thoughts come from, and why is the brain built to generate them in the first place?
Let us start by making a detour. Not into the depths of the meditating mind, but into a normal, everyday experience that may serve to illustrate important aspects of the wandering mind.
“Excuse me, could you repeat that question?” David asked at an important meeting at his work. They were discussing future strategies for his department, and the head of the office had asked him something. In an awkward moment, he realized that he had been absorbed in thoughts about an ongoing disagreement with his wife. He had missed his boss’s question. Late in the afternoon, while driving home from work, a new stream of thoughts ran through his head. He relived the awkward moment in his mind quite a few times, wondering if it would set him back in his ongoing competition with Ingrid, the young up-and-coming star of the department. After a while, though, his mind started to wander in other directions, touching on a number of past and future topics from his life, among them his son’s recent tardiness at school, the old cabin he used to go to with his grandparents when he was a boy, and the possibilities of a pay raise at work. His thoughts also returned to the conflict with his wife. All this was running through his mind while he was driving the car—steering, braking when needed, signaling when he turned, paying close attention to the cars around him.
This chain of mental activities shows some typical features of what experimental psychologists now call by many names, e.g., self-generated thought, stimulus-independent thought, task-unrelated thought, or mind wandering. These are thoughts we all have, unrelated to our immediate surroundings and the tasks at hand. For the most part, they deal with aspects of our own lives, including perspectives of the past and thoughts about the future. They arise spontaneously and last a few seconds before they change. Such spontaneous thoughts may be present on the fringe of our attention while we are doing other things, or they may take center stage in our minds and make us momentarily forget other things, competing with more task-related thinking. In the latter case, scientists call them mind wandering. They arise more often when we engage in routine tasks or have no immediate task at all, but they can also demand our attention while we try to do something important. Often, but not always, they will center on troublesome problems we need to solve.
Not surprisingly, this type of thought also enters the mind during meditation. This has been a topic for researchers in regard to several types of meditation, not least mindfulness meditation and nondirective meditation. There are no indications that there are any meditation techniques where such thoughts are not encountered. It is very common for meditators to regard such thoughts as distractions, diverting them from the task at hand, be it repetition of a meditation sound, following the breath, generating an inner, mental image, or other meditative tasks. In many meditation techniques, this view of spontaneous thought is taken at face value, so that reducing the frequency or duration of mind wandering is seen as a good thing, a long-term goal. On the other hand, teachers of most modern techniques will state that in the moment when any such thoughts arise in your mind, you should initially accept the thought before gently but firmly leaving it by returning attention to the primary meditation object, like your breath (Lutz et al., 2008; Brewer et al., 2011; https://mindfulpause.com/meditation-thoughts/). A group of techniques called nondirective meditation (see chapter 1) have as a common principle that not only should these thoughts initially be accepted, but that they even play an integral role in meditation itself and as such should not be minimized, provided they arrive or disappear spontaneously and not by an act of will. This deep-rooted acceptance of spontaneous mental activity is a condition for obtaining many of the psychological and physiological effects of nondirective meditation. In this regard, nondirective meditation is principally distinct from cognitive behavioral therapy, in which the patient is encouraged to take control of his or her mind wandering and avoid thoughts that are not deemed beneficial. Likewise, in many forms of mindfulness meditation, the meditator is encouraged to willfully terminate spontaneously arising thoughts after initially accepting their arrival in the mind.
Let us return to the brain. What can it tell us about the function of spontaneously occurring thoughts? First of all, our brain seems to be anatomically hardwired not only to engage in planned or willed or deliberate thoughts, but also to produce thoughts of a spontaneous, seemingly random kind. Let us return to David and his mind wandering to explore this.
Activity in distinct areas of David’s cortex, the half centimeter thick outer layer of his brain, represents all the different conscious tasks he does and his conscious emotions and senses. Different regions of his brain “fire” or signal in a coordinated fashion according to the exact task he is performing at any given moment, being it discussion at a meeting, driving a car, looking at a beautiful picture, repeating a meditation sound, or other activities. These are called primary cortical areas, see Figure 3.1. However, this is not the full picture. When we add up all these different task- or sensory-related areas, we still have significant regions of the cortex that are not allocated to specific, clear-cut functions. How do we use these parts of the cortex? Doctors have somewhat vaguely called them “association areas,” indicating that these areas may assist the primary cortical regions in finding out what they need to know in order to do their jobs. Association areas in the cortex may be used for higher cognitive functions such as attention, planning, or mind wandering.
Figure 3.1. Primary cortical areas are shaded in pink, signifying main areas involved with executing distinct tasks, such as moving the arm, or the perception of sensory information from the world around us. White areas represent the association cortex, which takes care of higher cognitive functions such as attention, planning, and mind wandering. (Figure designed by Freepik, modified by Tongtos Mahasuwan.)
In order to investigate in more detail how we use the task-unrelated regions of the brain’s cortex, we need to have in mind some peculiar facts about the brain. First of all, though the human brain is quite large compared to that of most other animals, it is still only about two percent of our total body weight. However, strangely enough, as much as 20 percent of the body’s blood flow is directed through the brain. This organ, then, is highly prioritized with respect to oxygen and energy supply. And how do we use our brain? For thinking, right? So it would be reasonable to assume that the more we think, the more oxygen and energy is consumed by the brain. However, already in the 1950s, Kety and co-workers at the University of Philadelphia showed that whether we sleep or are awake, whether we are idle or solve complex math problems, the brain uses almost the same amount of oxygen (Sokoloff, 1955; Mangold et al., 1955). When used for a certain cognitive task, the additional energy consumption associated with the resulting changes in brain activity is small, usually less than five percent in the area in question (Raichle & Mintun, 2006). A group of researchers led by neurologist and radiologist Marcus Raichle at the Washington University School of Medicine in St. Louis, Missouri, has pioneered research in the areas of the brain that are not evidently related to external tasks. Using PET scanning, they published a seminal article (Raichle et al., 2001) in the Proceedings of the National Academy of Sciences in 2001, where they examined which regions of the brain are activated or deactivated during attention-demanding and not-attention-demanding tasks, respectively. To their surprise, several areas of the cortex, mostly within the association areas, increased their activation when the brain stopped attending to demanding tasks. So when we perform certain tasks, like David above when he was taking part in the complicated discussion at the meeting in his department, many areas of the brain are activated. It is no surprise that these areas calm down when the task is done. After a task is completed, however, a system of other regions will increase their activity, most consistently during apparent rest or idleness. Raichle and his associates called what appeared to be a resting state the “default mode” of the brain, and thus, the network of regions activated while not engaging in external tasks was called the “default mode network.” Others have called it the “resting state network.” Several parts of this network are located in the medial part of the brain hemispheres, i.e., close to the midline of the brain; others are located laterally, more to the sides. Somewhat to Raichle’s surprise, the publication of these findings has received major scientific attention, with more than 6,000 scientific articles citing his article by June 2018.
The impact of Raichle’s research became significantly greater with the publication of a study from Dartmouth College by Malia Mason and coworkers, in 2007 in the journal Science (Mason et al., 2007). These researchers showed that the mental activity associated with the default mode network was stimulus-independent thought, or mind wandering, which we have discussed above. Numerous studies have also demonstrated default mode network activity, along with mind wandering, during meditation (see below).
What kind of thoughts are involved in mind wandering? This is still a focus for research, but we now know quite a bit about the thoughts that spontaneously fill our minds during rest. The type of thoughts clearly varies from person to person, though there seem to be several common characteristics. According to psychologists, most people report that their stimulus-independent thoughts are highly self-relevant, but also that they are moderately social in nature (Andrews-Hanna et al., 2013). They also say that their thoughts are moderately recurrent, somewhat goal-oriented, of moderate emotional intensity, and positive in mood. About three quarters of people’s spontaneous thoughts (77 percent) are about a particular event. Of the event-related thoughts, 60 percent are oriented toward future events, while 40 percent are about the past. Most of the future events are expected to take place in the near future (today or tomorrow). About 35 percent of us will spend quite a bit of time with imagery, i.e., thoughts with visual content, while half as many people will spend quite a bit of time with verbal thoughts, i.e., wordbased (Delamillieure et al., 2010). Most studies have shown that spontaneous thoughts tend to be associated with mildly positive emotions, and that they can help ease boredom; they are somewhat rewarding in themselves. Almost one quarter of us always mind-wanders about other people, and a bit more than half sometimes mind-wanders about others.
We still know too little about the characteristics of the spontaneous thoughts that occur during meditation, and to what degree different types of meditation may facilitate or reduce different types of mind wandering. However, mindfulness techniques are often believed to reduce mind wandering, while nondirective techniques like Acem Meditation have been shown to increase default mode network activity during meditation.
Not surprisingly, if the mind wanders while we are performing a task, such as counting, this will cause us to make more errors. On the other hand, people who have a high degree of openness to their inner lives, a preference for complexity and ambiguity, and a high tolerance for disorder and disarray, tend to be more creative (Barron, 1981). Likewise, allowing the mind to wander may facilitate creative problem solving (Baird et al., 2012). It has been claimed that spontaneous thought facilitates problem solving and learning (Baars, 2010).
Most scientists now believe that these thoughts have an adaptive function, i.e., they enable us to use spare time and brain capacity to spontaneously reflect on our recent experiences in an ever-changing social world, and thus help us to get along in our environment with success and less conflict with others. We use spare time to go through cognitive and emotional aspects of recent experiences in the social world in which we live.
Let us now look more closely into the default mode network in the brain.
The default mode network includes several interconnected areas of the brain cortex. Jessica Andrews-Hanna at the University of Arizona in Tucson is one of several researchers who study how these areas work together in certain ways. Their work now seems to indicate that the default mode network includes two subsystems, both of which communicate strongly with a common hub in the center (Andrews-Hanna et al., 2010). By combining input from the two subsystems—our personal memories and our relationships to others—and fitting these together with our emotions and evaluations, this hub continuously produces our experience of who we are at any given time in our social world.
As you may realize, these are highly demanding, complex processes. We live in a multifaceted, continuously changing social environment, which we constantly evaluate and react to emotionally. Remember David’s reactions to other people at work? Bringing it all together via the hub of the default mode network demands a high degree of computational power. In rats, this hub has been shown to contain the highest density of synapses, or connections between nerve cells, of the entire cortex (Valencia-Pesqueira, 2018). The same may be the case for humans, though we are not yet certain. However, the hub cannot do all of this processing alone. It acts in coordination with the two subsystems of the default mode network. We can call them the social subsystem (technically referred to as the dorsal medial subsystem), which is involved in the understanding of other people, and the autobiographical subsystem (technically referred to as the medial temporal subsystem), which is more concerned with what we did and experienced in the past and what we imagine we will do in the future.
Let us look more closely at how the different parts of the default mode network interact to accomplish these functions. In humans, the hub of the network actually consists of two regions of the cortex, both situated along the midline of the brain, one part in the front, one part further back. Together, they seem to deal with spontaneous (not controlled) thoughts about one’s self and others, and about past and future events. (See Figure 2 for an overview of the subsystem areas.)
However, the two parts of the hub mentioned above seem to be functionally somewhat distinct from each other. The front hub processes personal information, autobiographical memories, and future goals and events. It works closely with the back hub, which combines spontaneous attention with information from internal memory stores and perception of the outside world. The lower part of the back hub is specifically activated by spontaneous thoughts related to the self, to others, to memories from the past, and to thoughts about the future. The upper part of the back hub is active during spontaneous, involuntary awareness and arousal, as when attention is spontaneously caught up in mind wandering. This occurs regularly also during meditation.
This default mode network hub that combines activity in the front and back parts joins together information from the two subsystems of the network that we mentioned above: the social subsystem and the autobiographical subsystem. As our term indicates, the social subsystem is primarily occupied with thinking about others. One part of it is involved with the processing of social topics, like determining and inferring the intent of the actions of others. Another part continues along these lines, reflecting on the beliefs of others (Buckner & Carroll, 2007). This area provides us with the understanding that other people also have mental thoughts and feelings, just as we do—what is often called the “theory of mind.”
The autobiographical subsystem is believed to process memories of what we ourselves have experienced in the past, as well as what researchers call autobiographical “memories” of the future, i.e., envisioning future scenarios.
Figure 3.2. The social subsystem is marked with blue, the autobiographical subsystem with green, and the two parts of the central hub with yellow. The top brain hemisphere is seen from the left side, the bottom is the left hemisphere seen from the right side, from the midline rather than from the outside. (Figure designed by Tongtos Mahasuwan, based on Andrews-Hanna et al., 2010.)
Adding the roles of these three sets of default mode network structures together, we can formulate the function of the network as a whole in this way: the default mode network performs an automatic or spontaneous scan of information from two different dimensions—past and future, and self and others—allowing our attention to focus more strongly on what may in the moment be viewed as more relevant or important than other thoughts. Perhaps the underlying function of this is to make the attention of the brain revisit or reconsolidate synapses that have recently been activated, separating memories of insignificant episodes from emotional or stressful memories.
Nondirective meditation, then, can be seen as a mental technique that facilitates a spontaneous scanning of the brain for important past or future scenarios. This continuous sifting of mental content allows us to subconsciously re-evaluate memories, so that many of them may be forever left in the darkest parts of our brains’ mental storage rooms, while others may be stored in more accessible depositories, marked with relevant emotional tags that make them easy to find and use later on. Emotion is a useful regulator of perception and behavior, but emotion may also bind energy, in the sense that it requires mental energy to steer our behavior against the direction given by our emotions. One way of describing it would be to say that meditation may strip unnecessary emotional tags from many memories, while changing to more relevant emotional tags for other memories.
Having looked into the different units of this biological brain network and what it does, let us go back to the result in the mental world, as we experience it. All through the day, a steady stream of task-unrelated, spontaneous thoughts passes through our minds. It increases greatly when we relax or rest and will also appear in our minds at seemingly random intervals, even when we are deeply occupied with a task—just like what happened to David during his important department meeting. Long confined to a small, small corner in the outskirts of science, such spontaneous thought now constitutes an important field in modern psychological research. Though still young, this field tells us that mind wandering occupies somewhere between 30 and 50 percent of our waking time. These thoughts compete for our attention with our top-down task-related thoughts.
This competition is a source of error when we work on tasks, as David experienced during his momentary lack of attention at the meeting. However, we also seem to process emotions through these thoughts, and default mode network imbalances are thus linked to mood disorders such as depression or posttraumatic stress disorder. In spite of this, as discussed above, there are positive and important adaptive functions of such mind wandering, such as using spare time to consolidate and integrate past experiences so that we can adjust to a continuously changing social environment around us and make better plans for future actions. As discussed in detail in chapter 2, when outer challenges force us to minimize this mind wandering, we experience stress, exhaustion, and fatigue. Mind wandering is important—no wonder almost one third of our brain’s cortex is allocated to the default mode network!
Many years ago, a friend of mine said: “So you have learned to meditate? Then I guess you can empty your mind of all thoughts!” He was wrong, for two reasons. First of all, the technique I had just learned was Acem Meditation, where I was trained to accept and integrate my spontaneous thoughts and mind wandering in my meditation—not only allowing them to be present, but also to adjust to them, not fight them. Second, I don’t think anyone can really perform that trick, to empty one’s mind of all thought. I have never met a meditator who claimed to be able to do that. He or she would probably be dead. Quiet moments or stretches of silent time during meditation, yes, but the conscious experiencing of this silence is then a thought in itself. In fact, even during mindfulness meditation, where one attempts to minimize mind wandering, experienced meditators find themselves mind wandering on average every 80 seconds (Hasenkamp et al., 2012).
So there seem to be two ways to regard mind wandering in meditation. On one hand, such spontaneous thinking can be seen as a distraction from your meditation, taking your attention away from the mental task that gives physiological, psychological, or spiritual results. Such a view is represented by some meditation traditions, such as the chán (Chinese Zen Buddhist) practice of Silent Illumination. On the other hand, spontaneous thoughts may be seen to occur as a result or consequence of an optimal or good meditation practice. This more positive attitude to mind wandering is found in nondirective techniques like Acem Meditation. In Acem Meditation, spontaneous thoughts may even be seen as a necessary part of the process that leads to increased cognitive and emotional processing of past experiences.
There is no doubt that mind wandering occurs even during mindfulness meditation, but several scientists claim that this type of meditation ultimately serves to reduce mind wandering. What about nondirective meditation techniques? In one study of Acem Meditation published in 2014 (Xu et al., 2014), experienced meditators were scanned with fMRI as they meditated with a free mental attitude. Activation patterns were compared to those recorded during simple rest. Many areas of the brain differed in activation between the two situations—rest, or meditation with a free mental attitude. The main difference between the two situations was that many cortical areas were more strongly activated during meditation than during rest.
In what areas of the cortex was this increase during meditation recorded? Some areas represented repetition of the meditation sound, others the use of attention during meditation. But a large share of activated areas belonged to the default mode network, and a separate little brain area, the amygdala.
On the other hand, when the meditators were told to practice with concentration, using more force and effort to repeat the sound and not stray off into mind wandering, some areas still showed increased activation compared to rest. However, these areas were fewer and less strongly activated than during meditation with a free mental attitude. So nondirective meditation is more effective than directive meditation in activating the default mode network. Included in the strongly activated areas during nondirective meditation were in fact several areas that are known to play a role in the processing of emotion, such as the amygdala, the hippocampus, and the medial and orbital prefrontal cortex. So meditating with a free mental attitude seems to facilitate mind wandering per se, but very likely also emotional aspects of mind wandering.
Seen as a whole, we can now be fairly sure about four pieces of information: 1) The brain has allocated large parts of functional areas of the cortex to processing spontaneous thought. 2) These thoughts come intermittently all through the day, less often while we are engaged in demanding tasks, more often while we perform routine tasks or simply rest. 3) These thoughts seem to have important functions in processing or sifting through memories of the recent past, some of them of an emotional nature, in order to assist us when making good choices for the future. 4) Nondirective meditation may harness and build upon this brain processing activity, probably leading to decreased stress levels and to increased understanding of our relationships and our own lives.
Andrews-Hanna, J. R., Kaiser, R. H., Turner, A. E., Reineberg, A. E., Godinez, D., Dimidjian, S. & Banich, M. T. (2013). A penny for your thoughts: Dimensions of self-generated thought content and relationships with individual differences in emotional wellbeing. Frontiers in Psychology 4, article 900.
Andrews-Hanna, J. R., Reidler, J. S., Sepulcre, J., Poulin, R. & Buckner, R. L. (2010). Functional-anatomic fractionation of the brain’s default network. Neuron 65(4), pp. 550–562.
Baars, B. J. (2010). Spontaneous repetitive thoughts can be adaptive: Postscript on “mind wandering”. Psychological Bulletin 136(2), pp. 208–210.
Baird, B., Smallwood, J., Mrazek, M. D., Kam, J. W., Franklin, M. S. & Schooler, J. W. (2012). Inspired by distraction: Mind wandering facilitates creative incubation. Psychological Science 23(10), pp. 1117–1122.
Barron, F. & Harrington, D. M. (1981). Creativity, intelligence, and personality. Annual Review of Psychology 32, pp. 439–476.
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. Proceedings of the National Academy of Sciences of the United States of America 108(50), pp. 20254–20259.
Buckner, R. L. & Carroll, D. C. (2007). Self-projection and the brain. Trends in Cognitive Sciences, 11(2), pp. 49–57.
Delamillieure, P., Doucet, G., Mazoyer, B., Turbelin, M. R., Delcroix, N., Mellet, E., Zago, L., Crivello, F., Petit, L., Tzourio-Mazoyer, N. & Joliot, M. (2010). The resting state questionnaire: An introspective questionnaire for evaluation of inner experience during the conscious resting state. Brain Research Bulletin 81(6), pp. 565–573.
Hasenkamp, W., Wilson-Mendenhall, C. D., Duncan, E. & Barsalou L. W. (2012). Mind wandering and attention during focused meditation: A fine-grained temporal analysis of fluctuating cognitive states. Neuroimage 59(1), pp. 750–760.
Lutz, A., Slagter, H. A., Dunne.
J. D. & Davidson, R. J. (2008). Attention regulation and monitoring in meditation. Trends in Cognitive Sciences 12(4), pp. 163–169.
Mangold, R., Sokoloff, L., Conner, E., Kleinerman, J., Therman, P. O. & Kety, S. S. (1955). The effects of sleep and lack of sleep on the cerebral circulation and metabolism of normal young men. Journal of Clinical Investigation 34(7, Part 1), pp. 1092–1100.
Mason, M. F., Norton, M. I., Van Horn, J. D., Wegner, D. M., Grafton, S. T. & Macrae, C. N. (2007). Wandering minds: The default network and stimulus-independent thought. Science 315(5810), pp. 393–395.
Raichle, M. E., MacLeod, A. M., Snyder, A. Z., Powers, W. J., Gusnard, D. A. & Shulman, G. L. (2001). A default mode of brain function. Proceedings of the National Academy of Sciences of the United States of America 98(2), pp. 676–682.
Raichle, M. E. & Mintun, M. A. (2006). Brain work and brain imaging. Annual Review of Neuroscience 29, pp. 449–476.
Sokoloff, L.; Mongold, R.; Wechsler, R. L., Kenney, C. & Kety, S. S. (1955). The effect of mental arithmetic on cerebral circulation and metabolism. Journal of Clinical Investigation 34, pp. 1101–1108.
Valencia-Pesqueira, L. M.; Holst, R.; Hussain, S. & Davanger, S. (2018). Quantification of Spine Density in the Rat Default Mode Network. in prep.
Xu, J., Vik, A., Groote, I. R, Lagopoulos, J., Holen, A., Ellingsen Ø., Haberg, A. K. & Davanger, S. (2014). Nondirective meditation activates default mode network and areas associated with memory retrieval and emotional processing. Frontiers in Human Neuroscience 8: article 86.