“Honey, what are you thinking about?” asks my spouse as we sit at the kitchen table with our morning cups of coffee.
“Oh nothing,” I reply.
Our brains are fairly energy-intensive devices, consuming around 20 percent of the body’s energy, while making up only 2 percent of its mass. It has been known since the mid-1950s that the metabolic level of the brain hardly changes at all when it is actively engaged in a task – in other words, your brain stays active when you aren’t doing or thinking anything much.
This baseline background activity is the ‘default mode’. It arises from a network of brain areas discovered accidentally in the 1990’s, known as the “task-induced deactivation network”, or the Default Mode Network (DMN).
It turns out that the vast majority of the areas involved in the DMN overlap with areas that show up in brain studies of social cognition – making sense of ourselves and other people.
This is part of what psychologist Matthew Liebermann explores in Social – Why Our Brains Are Wired to Connect.
“When I first noticed the overlap between the default network and the social cognition network, I didn’t think it was particularly significant,”
“All this overlap tells us is that people typically have a strong interest in the social world and are likely to think about it when they have free time.”
But he later changed his mind about that and realized he had it backwards.
“I now believe we are interested in the social world because we are built to turn on the default network during our free time. In other words, if this network comes on like a reflex, it may nudge our attention toward the social world. And not just to other people as objects in our environment. Rather, the default network directs us to think about other people’s minds – their thoughts, feelings and goals.”
Almost 100 years after Swiss psychologist Jean Piaget, wrote that preschool children cannot consider what goes on in the minds of others, Libermann argues that the default mode network may provide our brains with thousands of hours of practice at decoding social interactions:
“You might be familiar with the claim that Malcom Gladwell made famous in his book Outliers that it takes 10,000 hours of practice to become an expert at something. Although different people might put those 10,000 hours toward becoming a concert violinist, professional athlete, or Xbox superstar, the brain puts in the 10,000 hours and more to enable us to become experts in the social world. One study found that 70 percent of the content in our conversations are social in nature.”
On the other hand, numerous studies have shown the 10,000 hour rule to be untrue. And not everyone agrees on the importance of the DMN.
Some argue that what neuroscientists are calling the resting state of the mind may just be the brain activity see when research participants are directed to do nothing in the noisy and claustrophobic inside of a brain scanner machine.
Others critics point out that since the brain’s metabolic level changes so little between tasks and resting, that the so-called default mode activity may be present during tasks as well and is consequently not a separate state at all. (Is it just me or do those two arguments cancel each other out?)
Dreaming And Meditating
To further complicate matters, the brain areas involved in the dmn are the same regions that are active when we are dreaming. Meditation has been linked with relatively reduced activity in the default mode network. Unless you are practicing Transcendental Meditation.
A 2016 study investigated experiences and brain patterns of students as they rested with eyes closed, during Transcendental Meditation practice, and while engaging in a challenging computer task. The study reported that activity in the default mode network remained high during Transcendental Meditation practice.
Activity in the default mode network is reported to go down in all other types of meditation – since they involve focus and control of the mind.
Since 2007, the number of research papers investigating the default mode network exploded, from 12 before 2007, to 1384 papers in 2014. There are even studies detailing the existence of a DMN in the brains of rats and monkeys.
Yet the question remains as to what exactly the brain is doing in the default resting state.
So, sorry. Until further notice, the answer to my spouse’s kitchen table question probably won’t change.
Footnotes: L. Sokoloff, R. Mangold, R. L. Wechsler, C. Kennedy, S. S. Kety. The effect of mental activity on cerebral circulation and metabolism. Journal of Clinical Investigation 34(7, Part 1):1101-8 · August 1955 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC438861/  A R Braun, T J Balkin, N J Wesenten, R E Carson, M Varga, P Baldwin, S Selbie, G Belenky, P Herscovitch, Regional cerebral blood flow throughout the sleep-wake cycle. An H2(15)O PET study., Brain, Volume 120, Issue 7, Jul 1997, Pages 1173–1197, https://doi.org/10.1093/brain/120.7.1173 https://academic.oup.com/brain/article/120/7/1173/304294  Frederick Travis, Niyazi Parim. Default mode network activation and Transcendental Meditation practice: Focused Attention or Automatic Self-transcending? Brain and Cognition
Volume 111, February 2017, Pages 86-94 https://www.sciencedirect.com/science/article/abs/pii/S0278262616300987