It has become common knowledge that some things—food, porn, outrage-share inducing articles—exploit a mismatch between our evolutionary heritage and the modern world, and do so at our expense. It seems, however, that we’ve collectively neglected one particular contemporary, omnipresent superstimulus: sound.

For a large proportion of my waking hours (70%?), sound is being directed straight into my eardrums. Not loud sound; I’m not worried about the health of my ears. Not “bad” sound; most of it is classical or electronic music, or ‘serious’ nonfiction audiobooks and podcasts. Yes, there’s a dash of delicious culture war content sprinkled among the podcasts and a healthy splash of music that might offend perhaps a 1980s Sunday school teacher, but I’m definitely not worried about the content.

What is starting to concern me, though, is the sheer lack of silence I experience in my daily life. Nothing specific is making me concerned, but it is gradually dawning on me that doing or consuming an excess of anything that was scarce in our ancestral environment, even the most benign music or informative nonfiction, can have a adverse effect on our mental and physical wellbeing.

Anyone listening?

While I am by no means the first to take notice, it isn’t like there’s an overwhelming amount of high-quality research and reporting on this. When I Google “Is silence important?” (the first phrase that came to mind, so not cherry-picking) plenty of listicles and a few other pop science articles come up: “7 Benefits of Silence,” “An Ode to Silence,” “10 Reasons Why Silence is Really Golden,” and “The Hidden Benefits of Silence,” to name a few. But the vast majority are some combination of poor quality and not actually about silence.

The first link, Google’s “featured snippet,” is a blog post by a soundproof enclosure company.

The second, Google’s first actual result, isn’t even about silence - it’s (mostly) about generalized hyperstimulation, stress reduction, and relaxation. Take, this paragraph, for instance:

“When we’re frazzled, our fight-or-flight response is on overload causing a host of problems,” says Dr. Sullivan. “We can use calm, quiet moments to tap into a different part of the nervous system that helps shut down our bodies’ physical response to stress.”

A lot of links cite the 2013 study Is silence golden? Effects of auditory stimuli and their absence on adult hippocampal neurogenesis, touting the finding that silence could stimulate neurogenesis but conveniently forget to mention that:

1. You guessed it:

      2. There’s a pretty good chance that adult human brains can’t even produce new neurons!

Not only do precious few rodent studies have anything meaningful to say about humans (see Are animal models predictive for humans?), but touting this study is akin to touting the finding that vitamin A consumption improves whisker quality. As just one example, this bullet appears in one article’s list of the health benefits of silence:

• Benefit brain chemistry by growing new cells. A 2013 study found that two hours of silence could create new cells in the hippocampus region, a brain area linked to learning, remembering, and emotions.

At least they linked to it.

Some are listening

That said, there are a few diamonds (eh, maybe quartzite) in the rough. Lifehack’s “Science Says Silence Is Much More Important To Our Brains Than We Think” at least refers to “a 2013 study on mice,” and ties together a few interesting lines of reasoning as to why silence itself might be beneficial, above and beyond mere relaxation.

A study [link added by me] published in the journal Heart discovered that two minutes of silence can prove to be even more relaxing than listening to “relaxing” music. They based these findings of changes they noticed in blood pressure and blood circulation in the brain.

Will it replicate? Who knows, but I’d bet on it. If you’d like to try for yourself, they used Beethoven’s Adagio molto e cantabile as the “soft classical” song. If this is true, the finding that silence produces a physiological effect distinct from relaxation is important and non-obvious.

While not really backing up the claim, the article also argues that

When you are not distracted by noise or goal-orientated tasks, there appears to be a quiet time that allows your conscious workspace to process things. During these periods of silence, your brain has the freedom it needs to discover its place in your internal and external world.

which intuitively seems correct.

This article in Nautilus features the unexpected and frankly fascinating findings that

While it’s clear that external silence can have tangible benefits, scientists are discovering that under the hoods of our skulls “there isn’t really such a thing as silence,” says Robert Zatorre, an expert on the neurology of sound. “In the absence of sound, the brain often tends to produce internal representations of sound.”

and

although intense cognition caused spikes in some parts of the brain, as you’d expect, it was also causing declines in the activity of other parts of the brain. There seemed to be a type of background brain activity that was most visible, paradoxically, when the test subject was in a quiet room, doing absolutely nothing.

[emphasis mine]

In the literature

I think I know why so many different articles all cite that 2013 mouse study: there isn’t a whole lot more to cite. When I try to find research on Google Scholar, using keyword combinations like “silence,” “quiet brain health,” “silence neuroscience” and the like, the vast majority of results are using “silence,” or “quiet” as a metaphorical descriptor:

Of these results, only the fourth is actually about an absence of sound. Even among the 60 papers that cite that 2013 study, I can find only two that actually compare the cognitive or physiological effects of silence and sound (first, second), and the latter is basically just a commentary on the virtues of introversion.

So, after maybe 45 minutes of digging around, I found three scientific studies on the subject matter, finding respectively that:

1. Silence promotes neurogenesis in mice (n=mice).
2. Silence induces lower physiological arousal than even calm music (n=24).
3. A bunch of rodent studies suggest that noise is a risk factor for Alzheimers and likely other neuro-psychiatric disorders.

I’m 110% sure that I’m missing most of the research out there (like those cited in the third bullet that I hadn’t seen), but I’m also 99.9% sure that there is way less research on silence than things like fasting, meditation, porn consumption (links to Google Scholar search results), and other contemporary superstimuli and efforts at their correction.

To be fair, there is quite a bit of research on loud sound, both in the context of ear health/hearing loss and of stress or other psychological effects, but virtually none of this seems applicable to the difference between silence/mild ambient noise, and normal, “intentional” sound like music or television.

Am I just making this up?

So far, I’ve leaned on my credentials as an armchair anthropologist, neuroscientist, and evolutionary biologist to assert that premodern people must have been exposed to silence more frequently than us. After thinking for about thirty seconds, there’s no way this is literally true. Birds chirp, leaves rustle. I can’t even comprehend how the typical caveman would have found near-total silence except by literally crawling deep inside a cave.

That said, it seems plausible to me that everything I’ve discussed so far isn’t really about silence, but about the absence of what I just referred to as “intentional” noise. Intuitively, it seems likely that there is a meaningful difference between hearing the sound of waves crashing, or rain, or wind blowing, and listening to soft classical music or a mellow conversation.

After all, music is designed to produce an emotional/aesthetic/psychological reaction, and speech is intended to transmit information. The birds outside don’t give a shit about how their chirps make us feel or what they make us think. So, there has to be something different going on in the brain between processing ambient, meaningless noise and something like speech or music.

Content or quantity?

While I am aware that natural sensory stimuli, including nature sounds, likely have a distinct, positive cognitive effect on us (in comparison to their absence), it is still very unclear to me how much of this benefit simply comes from giving our brains time away from “intentional” sound. For instance, what is the difference between hearing a gurgling creek and hearing a refrigerator quietly running in the background or cars occasionally pass outside? I have no idea.

Also, where is the border between “intentional” sound and whatever level and type of sound produces distinct cognitive benefits? Do we need complete silence? Seems unlikely, since our ancestors probably didn’t have access to it. Is a gurgling creek in fact “better” for the modern mind than the sound of a space heater? Maybe.

At what point does “music” turn into “ambient noise?” Is listening to the same soft piano song on repeat for hours more like hearing a new classical song, or more like leaves rustling in the wind? What about this hour-long, super mellow electronic piece that I put on for tasks requiring serious cognitive effort?

What I’m (not) doing

The notion that I might have a silence deficiency has been dawning on me over the course of maybe three or four months. One of the good things about writing things down, though (especially which I plan on making public), is crystalizes and clarifies what were vague notion in the back of my mind. When I made my list of book recommendations, simply writing “this recommendation applies to me, too” led me to actually read (well, listened to) the book in question.

Anyway, I’ve been making something of an intentional effort to listen to nothing as often as I can bear. The two most common occasions for this are driving and walking (I too have picked up this lockdown habit). Before, I would put on music, a podcast, or an audiobook virtually every single time I was in the car or on a walk. I still do, sometimes, but at least, eh, maybe 30% of the time I give my ears a rest.

Yes, I know this is pretty pathetic. I average 45 to 60 minutes of driving+walking a day, so this works out to something like 15 minutes a day, 1.75 hours a week, or 1.5% of my waking hours without any “intentional noise.” To my credit, this isn’t all the time I’m not listening to anything. I take my headphones off to do random stuff, eat, etc. But most of these things are consuming my general, non-auditory attention. Intuitively, it seems like silence should really “count” only when you would be able to listen intently to lyrical music or comprehend an audiobook, so walking and driving are in but, say, cooking a dish from a detailed recipe is out.

The phenomenology of silence

The sheer conscious experience (aka phenomenology, for us philosophy nerds) of silence is interesting, at least in comparison to the alternative.

Let’s say I’m on the 20 minute drive from my house to Earth Treks, my climbing gym. I’ve done the same drive down 495 probably at least a hundred times, so I’m on total autopilot. You should take the following report with a grain of salt, since introspecting and accurately reporting on one’s own conscious experience is likely difficult and plausibly impossible (check out illusionism), but I’ll try my best.

If I’m listening to something, it is generally a song I’ve heard quite a few times before, so I’m anticipating the coming melody and lyrics. Sometimes, my experience is “inside” the song, in that a good amount of my attention is directed to the notes and lyrics themselves. Other times, I will lose focus on the song and let my default mode network take the reins, my thoughts jumping without intentional direction between memories, concerns, plans, and other random bits of thought.

Now, let’s suppose I’m driving in silence. Not total silence, of course; the sound of the car itself is omnipresent. Nonetheless, it does not seem to be an object of my attention any more than a fan blowing in the background might be. Without a distraction or object of attention, my mind wanders in a similar fashion, but with more earnestness or intentionality, for lack of a better descriptor. Instead of flitting back and forth between the song and different, arbitrary thoughts, the thoughts tend to linger for longer and receive more attention

Often, some thought—a memory, a problem I’m trying to solve, something I have to do, whatever—doesn’t merely occur to me, but actively elicits “my” (what I perceive as my intentional, conscious mind or ego) participation. This can take the form of simple directed attention at the thought or a more active attempt to “manipulate” the thought in some way - perhaps by actively trying to solve some problem or making some sort of plan.

More interesting, and most peculiar to times of silence, is when some subconscious neural activity bubbles to the surface in the form of a sudden “insight” of some kind. This could come in response to some explicit intellectual project such as a research paper, but it is often much more mundane.

An example

Two days ago, after beginning to write this post, I went on a walk around my neighborhood sans headphones. The week prior, my (fully vaccinated) parents had gone on vacation, leaving my mostly-introverted self some delightful peace and quiet. Don’t get me wrong - my parents are fantastic and quite respectful, but there is a distinct cognitive load for us introverts associated with the omnipresence of other people, which for me makes it much harder to get into a Cal Newport-approved state of “deep work”-esque focus.

Anyway, walking around the neighborhood, it suddenly became clear that I should make the small amount of effort required to move my desk, chair, notebooks, and other materials to some more secluded part of my house. Not exactly a world-shattering insight, and one I certainly had all the information to come to without the need for deep introspection. Nonetheless, it seems overwhelmingly likely that the unprompted, sudden intuitive desire to do so was a direct result of giving my brain a few minutes without anything to do.

And so I am currently writing these words on a different floor from all other human beings, in my sister’s old bedroom-turned-makeshift-office (thanks Lindsay). Instead of getting up for the 12th time to turn off a light that someone just turned on or to close the door that someone just opened (both before leaving the room), I am staring out a window at the brownish-red leaves of the tree outside. All likely because I decided to forego listening to Travis Scott or (RIP) Juice WRLD (which if I recall correctly were my top artists of 2020 on Spotify) for the 1700th time.

Conclusion

In addition to staring at those rustling leaves, I am also writing these words while listening to Spotify’s Lo-Fi Beats playlist, my usual writing/working music alongside their Instrumental Study playlist. Am I losing something important by doing this? Would this post have been better written or more insightful if it had been written in silence?

I have no idea. Despite everything I’ve written so far, I am by no means convinced that soft classical and electronic music are going to be remembered as the corn syrup or canola oil of our ears. I’ll reiterate my list of questions a few paragraphs up:

Where is the border between “intentional” sound and whatever level and type of sound produces distinct cognitive benefits? What is the difference between hearing a gurgling creek and hearing a refrigerator quietly running in the background or cars occasionally pass outside?

Would going on my walk with Mozart instead of Mac Miller (also RIP) have led to the same insight as did going in silence? I can’t rerun the experiment, and I’d honestly put the odds around 1:1.

As a final bit of quarter-baked speculation, what’s the relationship between meditation—which has deservingly found its way into certain subcultures of the West—and mere absence of stimulation, auditory and otherwise? Is meditation to quiet what HIIT (high intensity interval training) is to less strenuous movement, or what 5,000 iu vitamin D supplements are to sunlight—that is, a concentrated megadose of something that used to be abundant?

These questions aren’t rhetorical, and I really would like to know the answers. For now, though, I’ll try to choose silence as much as I can. The music can wait.