The Wandering Mind
Neuroscientist Klaus Linkenkaer-Hansen discusses the biological reasons behind mind-wandering, the skill of attention control, and the role of AI in studying how the brain works.
What Is the Wandering Mind?
The wandering mind is a state where a person starts focusing on the contents of their own mind—on information they generate themselves—rather than on information coming from their senses. For example, when you’re driving or riding the subway, you might be so absorbed in your thoughts that you miss important external cues, even though you’re looking and listening. That’s how you might miss your stop.
This shift in attention can be triggered by something in the environment, but it can also happen spontaneously, without any sensory trigger. Neurophysiologists are interested in understanding why mind-wandering sometimes lasts just 5–10 seconds, while at other times it can go on for several minutes. What determines the duration of these episodes?
From a psychological perspective, boredom is the most common cause of a wandering mind. For instance, if you’re talking to someone who won’t stop rambling, you might get bored. It becomes hard to focus on their monologue, and you start entertaining yourself with your own thoughts.
Mind-wandering is a serious issue for workers engaged in simple but dangerous tasks, as it can lead to accidents. It’s also a challenge in education, when students can’t concentrate on the teacher or the book they’re reading.
History of Research: From James to Killingsworth
In the 1890s, psychology pioneer William James focused on studying the wandering mind and the stream of consciousness. He said, “While part of what we perceive comes through our senses from the outside world, another part (and it may be the larger part) always comes out of our own head.”
This statement was only recently confirmed by large-scale quantitative data in a landmark scientific paper by Matthew A. Killingsworth, published in 2011. This study was a game-changer and sparked new research into mind-wandering.
Killingsworth recruited 5,000 participants who downloaded a smartphone app so he could study changes in their wandering minds in real-life conditions. This approach differed from previous attempts, where participants filled out questionnaires throughout the day. When the app pinged at random times, participants answered three questions: “How do you feel right now?”, “What are you doing right now?”, and “Are you thinking about something unrelated to what you’re doing?” Out of a quarter-million responses, the rate of mind-wandering was a striking 47%. This was strong evidence for James’s claim.
Biological Causes of Mind-Wandering
A key and intriguing question is: can specific systems in the brain cause mind-wandering? The system most often implicated is the brain’s default mode network. It was discovered by Marcus Raichle and colleagues nearly 20 years ago during a meta-analysis using positron emission tomography (PET), which measures metabolic activity.
Researchers found decreased activity in certain brain regions whenever people were asked to perform a task requiring focus. This was surprising, as scientists previously assumed that cognitive tasks would increase brain activity. It turned out that there are core brain regions—located in the precentral and postcentral areas—with high baseline activity during rest, which decreases during tasks like solving math problems.
We still know little about the functional role of the default mode network. It’s usually studied using resting-state neuroimaging, where people are asked to sit still with their eyes closed (but not fall asleep) for 5–10 minutes. Unfortunately, only recently have we developed tools to measure the content and quality of thoughts and feelings during rest, and these tools are not yet standard in resting-state neuroimaging.
The Amsterdam Resting-State Questionnaire was specifically developed for this purpose and has been validated in studies involving over a thousand healthy participants. Research using this questionnaire has shown that there is large and stable individual variation in the thoughts and feelings of healthy people, but mental illnesses like depression and anxiety have a strong impact on thoughts and feelings during rest. We still have much work to do before we fully understand the neural correlates of mind-wandering during rest.
The large and stable variation in the content of mind-wandering suggests a genetic influence, which is an interesting and still unexplored topic. While Killingsworth found that, on average, people’s minds wander about 47% of their waking hours, this likely varies between 35% and 65% among individuals. Everyone needs internal processing and organization of information, but extroverts may spend less time on this than introverts.
How to Regain Control Over a Wandering Mind
Today in the West, there’s growing interest in mindfulness or attention-focused meditation, which is used to learn how to concentrate and reduce stress. During these exercises, people try to focus on a single object (such as the movement of the chest or the sensation of air passing through the nostrils while breathing) for 10–20 minutes. However, this can be boring, and an untrained person will constantly get caught up in their wandering mind. When someone notices they’ve become distracted, their attention should be brought back to the starting point.
The skill of attention control isn’t something you can master in a few minutes—it requires systematic daily practice over weeks and years. Only then is it possible to truly learn it. Such behavioral changes have been linked to improved mental health in cases of depression, anxiety, and post-traumatic stress disorder. Modern efforts are focused on understanding the neural mechanisms underlying these effects, as well as their impact on the content, quality, and frequency of mind-wandering episodes.
The Role of Artificial Intelligence in Brain Research
Neuroscience is currently experiencing a data explosion and rapid progress in digital signal processing, which is used to make sense of the data. Resting-state neuroimaging is just one example, as we now measure hundreds or thousands of time intervals, each originating from a tiny piece of brain tissue and showing extremely complex fluctuations. The job of a signal processing engineer is to quantitatively characterize these fluctuations and link them to neural mechanisms, cognitive phenomena, and behavior.
Alongside these developments, the field of computational neuroscience is growing. In other words, neural systems are modeled on computers, allowing for experiments with more precise control to study the role of specific mechanisms in brain dynamics. The challenge is to find the right level of measurement and description of human brain functions—from the molecular to the behavioral—and to connect experimental data with computational models so that we can ultimately understand how this complex and important phenomenon of mind-wandering works.
In fact, the amount of knowledge required may far exceed the capacity of any single person. Therefore, as more advanced artificial intelligence emerges—capable of working with unstructured data—we can’t rule out that it will play a crucial role in our understanding and data analysis of how the brain works.
Every year, new records show what machines can do better than humans. For example, 25 years ago, a computer beat the world chess champion. But chess is a fairly structured game. Later, AI beat the best players in Jeopardy!, and in 2016, it defeated the world champion in Go. IBM’s Watson system offered better cancer diagnoses than doctors could. With AI rapidly improving the ability of computing systems to make sense of data, it’s hard to say why these advances won’t surpass human abilities in absorbing vast amounts of information and making better decisions about how to understand the brain and treat its disorders.