Most of us are familiar with mind-wandering.

You’re sitting at your computer, or on a walk, or reading this article, and all of the sudden your mind is on something else completely, and it seems to have gotten there entirely of its own accord. If you are like most people, this happens to you once or several times a day, and you might not think much of it.

University of Virginia assistant philosophy professor Zachary Irving, though, has made a career of researching the phenomenon. Using a combination of philosophy and cognitive science, Irving studies what happens to our brains when our minds wander, why our minds wander, and why that might be important for better understanding both ordinary human thought processes and disordered thinking that can contribute to depression, anxiety or ADHD.

In his most recent paper, released in January, Irving and his co-authors identified an exact, 1.2-second electrophysiological signature of a subject’s stream of thought – or, what their brain looked like when their mind wandered.

What does your brain look like when you are not
consciously directing your thoughts?
UVA assistant professor Zachary Irving

“Essentially, we were able to get this short little window into what is going on in your mind,” Irving said. “What does your brain look like when you are not consciously directing your thoughts?”

To get there, Irving and co-author Julia W.Y. Kam hooked study participants up to EEG machines – or electroencephalography machines, which monitor brain activity – and had them do a simple, repetitive task, such as clicking a left or right arrow, for an hour. Every few minutes, the researchers would interrupt and ask participants questions about their thoughts. Were you ruminating on one thing? Were you directing your thoughts at all? Or was your mind freely wandering?

“It’s called thought sampling, a standard method for mind-wandering research,” Irving said. “We give you a boring task so that your mind can create this intrinsic stream of thought, and then we try to understand what is going on in your brain.”

The EEG machine tracked what a participant’s brain did when prompted by an arrow, and crucially, what it did in the window of time between the stimuli. By carefully timing the study, Irving and his colleagues could identify the brain activity associated with your internal stream of thoughts, rather than your responses to the outside world. Essentially, they could freeze the screen and capture what the brain is doing on its own, rather than how the brain was responding to the arrows.

“I got so excited when we found this window of internal activity,” Irving recalled. “It was brilliant.”

Studying the electrical picture of the brain at that moment, they noticed some important things. Perhaps most importantly, they noticed a pattern of what cognitive science researchers refer to as “intrinsic alpha power.” Alpha brain waves have been associated with imaginative, creative thought.

“We find a pattern that is really similar to what you find in creative thinking tasks,” Irving said. “That became a central part of our hypothesis, that mind-wandering is this meandering thought that is similar to the thought processes that underlie creative thinking. It fits intuitively, and now we had neural evidence to support that picture.”

The result also got at another question always on Irving’s mind: Why does the mind wander?

“One hypothesis I like is that mind-wandering serves the purpose of exploration. Without knowing it, you are generating creative ideas, or broadly exploring a base of ideas,” he said.

He offers up an analogy, first proposed by scholar Chandra S. Sripada: a rabbit foraging through a field, needing food. If the rabbit sticks to only one bush, he will soon deplete his supply of berries and he will miss out on other bushes in the field. In philosophy, this is referred to as a tradeoff between “exploration and exploitation.”

One hypothesis
I like is that
mind wandering serves
the purpose of exploration.
Without knowing it,
you are generating
creative ideas,
or broadly exploring a base of ideas.
UVA assistant professor Zachary Irving

“Our brains need a system to motivate us to explore,” Irving said. Just like the rabbits, we need to balance exploitation – using our brains to complete the tasks at hand – and exploration – thinking creatively and finding new ideas so that we can keep growing.

Mind-wandering, it’s important to note, is different from other forms of off-task thinking.

“If you are distracted in class, your mind could be doing all sorts of different things. You could be fixating on something, maybe obsessing about a fight you just had with your friend, or directing your thoughts to another task,” Irving said. In that case, your mind is not really wandering – it’s just focused on something else.

“To me, the most central quality of mind-wandering is it’s dynamic – you are not guiding your mind to remain on one topic … those deliberate constraints are gone, and the absence of those constraints generate a meandering stream of thought.”

Now in possession of a neural signature of those moments of dynamic, task-unrelated thought, Irving and his colleagues have been able to compare them to several clinical disorders and spot important similarities and differences

“Past research has shown that there is a relationship between task-unrelated thought and a whole host of clinical disorders,” Irving said. “People who are depressed or anxious tend to have more task-unrelated thought, and it also seems to be a common factor in ADHD [attention-deficit hyperactivity disorder] and OCD [obsessive-compulsive disorder].”

However, Irving said, it is important to differentiate between the ruminative, fixated thought typically associated with anxiety and depression and the meandering thought that is a hallmark of ADHD.

“You need to examine not just if someone is disengaged with the outside world, but what is actually going on inside their brain,” he said. “Our long-term goal is to be able to measure these different categories of thought.”

Those measurements would help health care providers more easily distinguish between different disorders, based both on the thought patterns patients report and the electrophysiological signatures evident in their brain.

“We don’t want to move beyond self-reporting, but to supplement it and track how your brain behaves over time,” he said. “It still feels kind of like science fiction to me, but it is a real, achievable and exciting goal.”

Another goal Irving is excited about? Helping people let their minds wander on purpose. Already, he said, we do this intuitively – perhaps by taking a walk when we are stumped by a problem.

“Artists are really good at this, and often report letting their minds wander for long periods of time,” he said. “It’s also a common idea in certain strands of Buddhism.”

One future application could involve using technology to alert someone when their mind wanders, and to either suppress or foster mind-wandering.

“To me, that is a fascinating possibility to think about,” Irving said. “Again, it sounds kind of like science fiction, but is also very achievable.”