The default mode network isn't idle. It's expensive. That single finding, which came out of a lab at Washington University around 2001 and has been argued over ever since, rearranges what boredom is, and I think most of us are still running the old model.

The brain does not rest

Marcus Raichle and colleagues were doing brain imaging with the usual method: give someone a task, measure which regions light up, subtract the "resting" baseline. What they noticed was that the baseline was not a baseline. When subjects lay in the scanner doing nothing, a consistent set of regions, the medial prefrontal cortex, the posterior cingulate, parts of the parietal lobe, increased their activity, and then went quiet the moment a task started.

They called it the default mode network, and the first surprising fact about it is the cost. The brain is about 2% of body mass and uses about 20% of resting energy, and the amount of that budget that changes when you go from resting to concentrating hard is small, on the order of 5%. The lights are almost all on, all the time. Rest turns out to be a different program running on the same hardware at nearly the same wattage.

The second surprising fact is what the program is doing. The default mode network is most active during mind-wandering, autobiographical memory, imagining the future, and thinking about other people's mental states. It is, roughly, the simulator. When there's no task, the brain doesn't stop. It starts running scenarios.

So what is boredom

If the resting brain is busy, boredom cannot be the experience of the brain having nothing to do. It has plenty to do. It's doing it. Boredom is something else.

The cleanest account I've found is from John Eastwood and colleagues, who define boredom as the aversive state of wanting to engage in satisfying activity and being unable to. Not the absence of stimulation. The failure to find anything worth allocating attention to. You have the attention. It's available. Nothing in the environment, or in your own head, is clearing the bar to get it, and the unspent attention is what you feel.

That makes boredom a signal, the same way hunger is a signal. Hunger doesn't mean the stomach is empty. It means the body has computed that acquiring food is now worth more than whatever you are doing. Boredom means the brain has computed that whatever you're attending to is worth less than the expected value of attending to something else, and it does not know what the something else is yet. It is an opportunity-cost alarm with no target.

The shock experiment

The strongest evidence that boredom is aversive in its own right, and not just neutral, comes from a study Timothy Wilson's group published in 2014. They put people alone in a room for fifteen minutes with nothing to do but think. Most reported it was unpleasant. Then, in a follow-up, they gave subjects the option of giving themselves a mild electric shock, one they had earlier said they would pay to avoid, as the only available activity.

About two thirds of the men and a quarter of the women shocked themselves at least once. One man did it 190 times.

The usual reading is that people are bad at being alone with their thoughts. I think the sharper reading is that the alarm is loud enough that people will do almost anything to answer it, including things they know are worse than nothing. An empty room turns the signal up and provides no target, and the shock is a target. It's a bad one. It's still a target.

What the signal is for

If boredom is a signal, it should have a function, and the candidate is exploration.

Any organism that can learn faces a trade-off between exploiting what it knows and exploring for something better. Stay in the productive patch or wander. Reinforcement learning has the same problem and a whole family of strategies for it. Boredom looks a lot like the biological version: a rising cost on the current activity, proportional to how little new information it is yielding, that eventually makes leaving cheaper than staying.

That fits the phenomenology. Boredom is not what you feel when you're learning. A hard problem isn't boring. A repetitive task is, because it has stopped producing prediction error, and a brain that isn't being surprised is a brain being told to go find something that will surprise it. The default mode network is presumably part of the search: it starts generating scenarios, memories, plans, candidates for what to do instead.

Which means the productive move, when bored, is to let the search run. Most of the accounts of insight arriving in the shower, on the walk, in the boring meeting, are reports of the default mode network producing a candidate that the task-focused brain hadn't been able to reach.

Disabling the light

Here's where the phone comes in, and I'll try not to moralize.

The phone is, among other things, the most effective boredom suppressant ever built. It's always a target. It always clears the bar, because it has been tuned by a great many engineers to clear the bar. The moment the alarm goes off, you reach for it, and the alarm stops.

The problem isn't that this is pleasant. It's that it disconnects the signal from its function. Boredom was supposed to push you toward the search. The phone answers the signal without running the search. It's a check-engine light that you can turn off by pressing it, and after a while you stop knowing what the engine was trying to say.

There's early research suggesting that people who reach for the phone at the first sign of boredom report more boredom overall, not less, which is the pattern you would expect if the signal is being suppressed rather than resolved. The alarm keeps going off because the underlying condition, a brain that wants a better allocation, was never addressed. It was just muted.

Using it

I have been treating boredom differently since I internalized this, and the change is small.

I try not to reach for anything in the first minute. That's roughly the time it takes for the default mode network to spin up and start producing candidates. The candidates are usually mundane, a thing I forgot to do, a person I should call, and occasionally one is the answer to a problem I had stopped working on, which is the entire payoff.

I try to notice which activity is producing the boredom, because the signal is usually accurate. If a meeting is boring, the meeting is not yielding information. That is data about the meeting.

And I try to remember that the cost of the search is nearly free. The network is running anyway. The wattage is spent whether or not I let it do its job. Boredom is just the part of the brain that plans, asking to be allowed to.