Content 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. The 60-cycle hum of power lines is audible, although we habituate to it. We can hear 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.
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.
- Science says silence is much more important to our brains than we thought
- Studies show the importance of silence and how it positively affects your brain’s development
- This is your brain on silence
All of the above cite a particular study from 2013 as part of their arguments:
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.
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. In real life, we almost always perceive some reflected sound. Any noise would without reflection sounds “dead.”
This is a highly disturbing auditory situation if you don’t understand what is going on. I’ve been in an environment that approximates that. It makes your ears feel funny and you lose senses you didn’t even know you had. You can no longer sense where objects are in relation to your body (the rudimentary human equivalent of echolocation).
For mice, being trapped in an anechoic chamber and exposed to its unique qualities could well have stressed them out of their minds. We can’t explain it to them. 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.
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!
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Copyright 2016 Eileen Anderson