Silence is…Scary?

Trigger warning: animal experimentation (mice).

This post is not directly about dogs, but it’s about something we see happening in the dog world very frequently. That is the misunderstanding and misapplication of research results. This particular example caught my attention because it involves something I have a bit of expertise in: sound.

In the past few years there has been a rash of articles about how important silence can be in our lives. Many of them center on a campaign by the Finnish Tourist Board that promoted the restful silence of that country. I’ve been there, and it’s true!

The silence thing got my attention. I’m a fan. I’m an auditory person, musically trained. I’m very sensitive to my auditory environment and dislike unnecessary background noise, including music. When I have music, radio, or the television on, I am actively listening.  When I’m done they go off. I need and enjoy quiet.

Likewise I am quite attuned to the “background” sounds that are present even when it’s very quiet. I am sitting in my study now. I’m aware of traffic noises, neighborhood dogs, the occasional creak of the house, the furnace and refrigerator when they cycle on, my neighbor’s sump pump, and Clara snoring. She’s got a funny little whistle sound in her nose. Plus I can hear some of the common urban mashup of low frequency noises. There is the 60-cycle hum of power lines and even lower frequencies generated by industrial equipment. Most of us city dwellers are unaware of these lower frequency, deeper noises, although sometimes we notice their absence if we get out “beyond the sidewalks,” especially at night. But even with all that going on, my environment right now definitely qualifies as quiet, if not exactly silent.

Frequency and magnitude breakdown (FFT) of the noise in my study

Frequency and magnitude breakdown (FFT) of the noise in my study

How different would it feel if **all** that noise were gone?

Silence is Golden?

The articles I ran across praised the value of silence in our lives and cited a scientific study that had “proved” the value of silence.

Here are some of the articles.

All of the above cite a particular study from 2013 as part of their arguments:

Is silence golden? Effects of auditory stimuli and their absence on adult hippocampal neurogenesis

The entire study is available at the link.

In the study, the effects of different auditory stimuli were tested on mice with the goal of analyzing whether they affected the creation of new brain cells. The scientists were looking at adult neurogenesis in the hippocampus. They exposed the mice to five different acoustic conditions: the ambient sounds of the facility, white noise, some Mozart piano music (thoughtfully transposed to the normal hearing range of the mice), the calls of rat pups, and silence. Most mice were exposed to one of the auditory stimuli for two hours a day for three days inside an anechoic chamber. After one more day they were killed and their brains were studied. Some mice were exposed for seven days, then killed.

The Mozart music and the silence resulted in the largest increase in precursor cell proliferation after three days of exposure to the sounds. (Precursor cells are new, blank cells that can develop into different kinds of cells. For example, stem cells are one type of precursor cell.) And after seven days of exposure, only silence was associated with increased numbers of precursor cells. Edit 4/3/16: I deleted some incorrect comments I made about the control of the study. 

Back to the articles. They claim, and cite this study to support, the idea that periods of quiet, perhaps “down time,” are beneficial to our brains. The articles evoke images of calm contemplation and taking breaks from mental activity. This is a potent meme in our sometimes noisy, frenetic lives.

Such periods probably are beneficial. The problem is that that is not what this study is about. The term “silence” in the study refers to a specific state that is virtually never replicated in normal life. And it was probably not a pleasant state for the experimental mice, despite the article title. Here’s what it really involved.

Anechoic Chambers

the walls of an anechoic chamber absorb sound and break up the waves, creating and eerie silence

Walls of anechoic chamber–photo source, Wikimedia Commons

All of the mice experienced the sound exposure inside an anechoic chamber. Anechoic chambers are enclosed spaces in which the amount of reflected sound is reduced almost to zero. They are built of absorptive material installed in patterns designed to break up sound waves. They are also insulated from exterior noise. When there is sound being generated on the inside, as with the recordings used in the experiment, only the original sound wave reaches the organism’s ears. There are no reflections. This is an abnormal situation because in real life there is virtually always some reflection. Any noise would sound “dead.”

This is a highly disturbing auditory situation. Here is an article about the effects on humans in a very well designed anechoic chamber:

We all crave it, but can you stand the silence? The longest anyone can bear Earth’s quietest place is 45 minutes  **See addendum at bottom of post

Perhaps the mice didn’t hallucinate, as some humans are known to do, but being trapped in an anechoic chamber and exposed to its unique qualities could well have stressed them out of their minds. So we need to get rid of the positive connotations of the word “silence” in the case of this study. This was not restful or calm. It was foreign and strange, something that no animal could be prepared for from previous life experience.

We should note that the mice who were exposed to other auditory stimuli were also placed in the anechoic chamber. There was doubtless also some strangeness for them. But since sound was being played, they would not experience the strangeness of absolute silence.

The Results

If you read far enough in the study, there is discussion about silence being a stressful state.

But of the tested paradigms, silence might be the most arousing, because it is highly atypical under wild conditions and must thus be perceived as alerting. Functional imaging studies indicate that trying to hear in silence activates the auditory cortex, putting “the sound of silence”, the absence of expected sound, at the same level with actual sounds. The alert elicited by such unnatural silence might stimulate neurogenesis as preparation for future cognitive challenges.–Kirste, Imke, et al. “Is silence golden? Effects of auditory stimuli and their absence on adult hippocampal neurogenesis.” Brain Structure and Function 220.2 (2015): 1221-1228.

No kidding. In other words, the level of silence was novel and probably uncomfortable and scary. The apparent increase in neurogenesis in the mice’s brains correlated with a time when they were suddenly thrust into an eerily quite, unnatural environment and couldn’t escape. They weren’t in the equivalent of a pleasant, peaceful, mousie yoga studio.

A more accurate title for an article about this study might be, “Being trapped without the possibility of escape in a strange, frightening environment may help generate new brain cells.”

The Big Picture

I am not weighing in on the methods and results of the study. Neither am I arguing against the value of relative quiet in our noisy human lives. I am highlighting the way this study is being incorrectly referenced. The results of the study do not connect with the spin of the articles about it. And we can’t blame it only on the journalists. Note that the scientists themselves prompted this, in part, with the reference to “Silence is golden” in the title. Catchy, but misleading. (Also, to be fair, most of the articles cite other studies as well, studies that may support the claims about restful silence.)

Humans love to take mental shortcuts, and articles about the “value of quiet” are attractive in our noisy, hasty world. They resonate, if I may use another auditory figure of speech. But we need to be careful.

This particular example jumped out at me since I have a background in acoustics. I was curious about how the “silence” was created, and as soon as I saw the mention of an anechoic chamber, I was on the trail. But in this study, you don’t actually have to understand acoustics to see the problem, as long as you read the whole thing. The paragraph I quoted above is one of several in the “Discussion” part of the study where they make observations and theorize about the findings. The fact that the silence was a highly stressful condition is discussed in detail. But you have to read far enough to get there, and to drop your automatic warm fuzzy thoughts about silence and calm states.

I’d love to know whether anyone has been in an anechoic chamber or experienced other sensory deprivation. What was it like? When I was in graduate school we bought the materials to build a chamber and I messed around with the stuff, so I know what even a small exposure to the noise absorptive materials made my ears feel like. Creepy!

Related Posts

Don’t Get Mud On Your Face! Citing Research in Discussions 

Reading Research: 8 Classic Red Flags (Yvette Van Veen of Awesome Dogs)

Reading Research: Does Size Matter? (Yvette Van Veen of Awesome Dogs)

How to Spot Research Spin: The Case of the Not So Simple Abstract

**So the joke is on me. In a post about being cautious about the spin of research and articles, I included an article with a questionable claim myself. The article about the anechoic chamber in Minneapolis includes the claim that no one can “survive” longer than 45 minutes in the chamber.  Some cursory consideration would indicate that there is no magic difference between 45:00 and 45:01, and that anechoic chambers are not killing machines. Indeed, there is a “myth-busting” type video documenting a man who stayed in the anechoic chamber about an hour with no ill effects. Reader Paul McGee provided a link in the comments. I picked an article that could give people a sense about anechoic chambers, and there’s not much question that they are strange and unpleasant for most people. The 45 minutes thing is a silly claim though.

Copyright 2016 Eileen Anderson

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6 Responses to Silence is…Scary?

  1. meganlyra says:

    When I was growing up, my mother had a “sensory deprivation” tank. Such things were in vogue for a while; I’m not sure if they still exist. It was long and black; to me it looked like a chunky coffin. The walls and door were thickly insulated. You got inside and floated in saltwater, the idea being that you limited your senses (apart from smell!) as much as possible: i.e., your body felt no hard surface, it was pitch dark, and you heard nothing except a very muted rushing noise in your head. I tried it once (age 11 or 12). I hated it, which in retrospect I find interesting. I am highly sensitive to noise and light: e.g., I often find tv stressful to watch, and there are some shops I have to leave because of a high pitch that puts pressure on my brain (or that is what it feels like). So I ought to have enjoyed an hour of silence! But it only made me anxious — so I feel for the mice 🙂

    • Eileen Anderson says:

      Hi Megan, Thanks for sharing that experience. Those things seem to come in and out of vogue for humans. I think I would be attracted to the anechoic chamber idea except that I know what it “feels” like against one’s ears. Not the same as natural quiet at all. Thanks for commenting!

  2. Paul McGee says:

    Anechoic chamber not so disturbing, perhaps. https://www.youtube.com/watch?v=mXVGIb3bzHI

    • Eileen Anderson says:

      Interesting! Thanks for the contrast to the article and claims about this chamber.

  3. laura says:

    i spent time in a sensory deprivation tank as a journalist some years ago. I didn’t find it unpleasant, but i did start some vivid awake-dreaming. I knew i was awake but i was seeing things. I think the mind invents stimulus when none is available. Or something. Anyway I can tell you i was in it for 2 hours but it felt like half an hour.

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