The Frontal Cortex

An interesting new study on mind-wandering and the default network was recently published in PNAS. The scientists, led by Kalina Christoff of UBC and Jonathan Schooler of UCSB, used "experience sampling" in an fMRI machine to capture the moment of daydreaming: essentially, subjects were given an extremely tedious task and, when their mind started to wander (this was confirmed with subjective reports and measurements of task performance), had changes in their brain activity recorded in the scanner. It's been known for nearly a decade that daydreaming is a metabolically intense mental process, but this latest study further clarifies the sequence of events:

Activation in medial prefrontal default network regions was observed both in association with subjective self-reports of mind wandering and an independent behavioral measure (performance errors on the concurrent task). In addition to default network activation, mind wandering was associated with executive network recruitment, a finding predicted by behavioral theories of off-task thought and its relation to executive resources. Finally, neural recruitment in both default and executive network regions was strongest when subjects were unaware of their own mind wandering, suggesting that mind wandering is most pronounced when it lacks meta-awareness. The observed parallel recruitment of executive and default network regions--two brain systems that so far have been assumed to work in opposition--suggests that mind wandering may evoke a unique mental state that may allow otherwise opposing networks to work in cooperation.

Last year, I wrote about the surprising benefits of thinking with the default network, which seems to be an important element of creativity:

In recent years, however, scientists have begun to see the act of daydreaming very differently. They've demonstrated that daydreaming is a fundamental feature of the human mind - so fundamental, in fact, that it's often referred to as our "default" mode of thought. Many scientists argue that daydreaming is a crucial tool for creativity, a thought process that allows the brain to make new associations and connections. Instead of focusing on our immediate surroundings - such as the message of a church sermon - the daydreaming mind is free to engage in abstract thought and imaginative ramblings. As a result, we're able to imagine things that don't actually exist.

"If your mind didn't wander, then you'd be largely shackled to whatever you are doing right now," says Jonathan Schooler, a psychologist at the University of California, Santa Barbara. "But instead you can engage in mental time travel and other kinds of simulation. During a daydream, your thoughts are really unbounded."

The ability to think abstractly that flourishes during daydreams also has important social benefits. Mostly, what we daydream about is each other, as the mind retrieves memories, contemplates "what if" scenarios, and thinks about how it should behave in the future. In this sense, the content of daydreams often resembles a soap opera, with people reflecting on social interactions both real and make-believe. We can leave behind the world as it is and start imagining the world as it might be, if only we hadn't lost our temper, or had superpowers, or were sipping a daiquiri on a Caribbean beach. It is this ability to tune out the present moment and contemplate the make-believe that separates the human mind from every other.

I think Virginia Woolf, in her novel To The Lighthouse, has a particularly fine description of this mental process as it unfolds inside the mind of a character named Lily:

Certainly she was losing consciousness of the outer things. And as she lost consciousness of outer things, her mind kept throwing things up from its depths, scenes and names, sayings, memories and ideas, life a fountain spurting over that glaring, hideously difficult white space.

A daydream is that "fountain spurting," as the brain mixes together ideas, memories and concepts that are normally filed away in discrete mental folders.