You’re sitting at your desk, gazing out the window, your mind wandering. Instead of getting on with what the work you are supposed to be doing, you start mentally planning your next holiday or find yourself lost in a thought or a memory.
It’s only later that you realize what has happened: Your brain has just changed channels- and switched to autopilot.
What’s that all about?
When you are solving a mental puzzle, your brain’s control network for outward focused, goal-oriented thinking is activated. At the same time, your brain’s network for inward focused thinking like daydreaming must be turned down to avoid interference.
Or so scientists thought.
Now, research from Cornell University shows that engaging brain areas linked to so-called “off-task” mental activities, like mind-wandering and reminiscing, can actually boost performance on some mental tasks.
“The prevailing view is that activating brain regions referred to as the default network impairs performance on attention-demanding tasks because this network is associated with behaviors such as mind-wandering,” said neuroscientist Nathan Spreng, study leader. “Our study is the first to demonstrate the opposite – that engaging the default network can also improve performance.”
True to its name, the default mode network seems to become active in the absence of external influences. In other words, the anatomical structure of the brain seems to have a built-in autopilot setting.
The default mode should not, however, be confused with an idle state. On the contrary, daydreaming, imagination, and self-referential thought are complex tasks for the brain.
The results advance the understanding of how externally and internally focused neural networks interact to facilitate complex thought, the researchers say.
Many neuroimaging studies have already shown that default network activation interferes with complex mental tasks.
But in most of the studies, Spreng says, the mental processes linked with default network conflict with task goals. If you start thinking about what you did last weekend while taking notes during a lecture, for example, your note-taking and ability to keep up will suffer.
An Interconnected and Anatomically Defined Brain System
In Spreng and his colleagues’ new approach, off-task processes such as reminiscing can support rather than conflict with the aims of the experimental task.
Their unique task, “famous faces n-back,” tests whether accessing long-term memory about famous people, which typically engages default network brain regions, can support short-term memory performance, which typically engages executive control regions.
While having their brains scanned, 36 young adults looked at sets of famous and anonymous faces in sequence and were asked to identify whether the current face matched the one presented two faces back.
The team discovered that participants were faster and more accurate when matching famous faces than when matching anonymous faces and that this better short-term memory performance was associated with greater activity in the default network.
These results show that activity in the default brain regions can support performance on goal-directed tasks when task demands align with processes supported by the default network, the authors say.
The default mode network is an interconnected and anatomically defined brain system that activates when individuals engage in internal tasks such as daydreaming, envisioning the future, retrieving memories, and gauging others' perspectives.
Its subsystems include part of the medial temporal lobe for memory, part of the medial prefrontal cortex for theory of mind, and the posterior cingulate cortex for integration, along with the adjacent ventral precuneus, and the medial, lateral and inferior parietal cortex.
Precise Function Remains Unclear
“Outside the laboratory, pursuing goals involves processing information filled with personal meaning – knowledge about past experiences, motivations, future plans and social context,” Spreng said. “Our study suggests that the default network and executive control networks dynamically interact to facilitate an ongoing dialogue between the pursuit of external goals and internal meaning.”
The default mode network is a network of brain regions that are active when the individual is not focused on the outside world and the brain is at wakeful rest.
Also called the default network, default state network, or task-negative network, the default mode network (DMN) is characterized by coherent neuronal oscillations at a rate lower than 0.1 Hz (one every ten seconds).
During goal-oriented activity, the DMN is deactivated and another network, the task-positive network (TPN) is activated. The DMN may correspond to task-independent introspection, or self-referential thought, while the TPN corresponds to action.
The precise function of the default mode network remains unclear, however, acitivity in the network negatively correlates with activity in regions involved in attention and executive function. In humans, the default mode network has been hypothesized to generate spontaneous thoughts during mind-wandering and may relate to creativity.
Worried that you’re not Daydreaming enough?
In 2010, Harvard scientists Matthew Killingsworth and Daniel Gilbert developed an iPhone app that captured user’s feelings in real time. The tool alerts the user at random times and asks: “How are you feeling right now?” and “What are you doing right now?
Killingsworth and Gilbert’s analysis suggested that mind-wandering was much more typical in daily activities than in laboratory settings. Surprisingly, they also observed that people were less happy when their minds were wandering than when they were otherwise occupied.
This effect was somewhat counteracted by people’s tendency to mind-wander to happy topics, but unhappy mind-wandering was more likely to be rated as more unpleasant than other activities.
The authors note that unhappy moods can also cause mind-wandering, but the time-lags between mind-wandering and mood suggests that mind-wandering itself can also lead to negative moods.
Reasearch also suggests that regardless of working memory capacity, participants participating in mind wandering experiments report more mind wandering when bored, stressed, or unhappy.
R. N. Spreng, E. DuPre, D. Selarka, J. Garcia, S. Gojkovic, J. Mildner, W.-M. Luh, G. R. Turner. Goal-Congruent Default Network Activity Facilitates Cognitive Control. Journal of Neuroscience, 2014; 34 (42): 14108 DOI: 10.1523/JNEUROSCI.2815-14.2014
Baird, B.; Smallwood, J.; Mrazek, M. D.; Kam, J. W. Y.; Franklin, M. S.; Schooler, J. W. (2012). “Inspired by Distraction: Mind Wandering Facilitates Creative Incubation”. Psychological Science 23 (10): 1117–1122.
Matthew A. Killingsworth and Daniel T. Gilbert (2010). “A Wandering Mind Is an Unhappy Mind”. Science 330 (932).doi:10.1126/science.1192439. PMID 21071660.