Why Do Some People Hate Sounds Like Chewing?

We all find some sounds annoying, but for people with misophonia, certain sounds trigger strong feelings of anger and anxiety. Learn what researchers think causes this in today's episode of BrainStuff, based on this article: https://science.howstuffworks.com/life/inside-the-mind/human-brain/why-do-some-people-hate-the-sound-chewing-scientists-might-have-the-answer.htm

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Episode Transcript

Speaker 1 (00:01):
Welcome to brain Stuff, a production of iHeartRadio, Hey, brain
Stuff Lo and Vohla bamb Here. It's dinner time with
the family, and everyone's eating and chatting any family drama aside.
It sounds like a good time, right, But for some,
hearing other people's crunching, lip smacking, or gulping can cause

(00:24):
anger and anxiety. Miss Aphonia is a condition that often
evokes strong negative feelings at a person in response to
certain sounds, from other people's eating and drinking, to pen
clicking and keyboard tapping to simple breathing, so much so
that they have to get away from the source of
those sounds. But science is working on it. Back in

(00:48):
twenty seventeen, research published in the journal Current Biology studied
the brains of people with missophonia to see how their
brains process emotions after hearing certain sounds. Evaluated the data
of forty two participants, a twenty with missophonia and twenty
two without. People who don't have missophonia can generally tune
out everyday sounds that might be a bit bothersome. For

(01:12):
people with missophonia, the sensitivity comes from the pattern of
the sound, though not its volume. For the article, this
episode is based on how stuff works. Spoke with study
co author doctor Subinder Kumar, now a research assistant professor
of neurosurgery at the University of Iowa. He explained that
the aversion to certain sounds is quote a sudden realization

(01:35):
on the part of the person who has missophonia. They
just can't tolerate the sound and it just goes on
and on over time. While it's not known exactly how
common the condition is, it can be debilitating for the
people who do have it. On average, symptoms start around
age twelve, but they can appear as early as age five.

(01:56):
Trigger sounds often incite rage and anxiety. The sensitivity can
get so intense that a person might lash out verbally
in response to a sound or begin avoiding social situations
where the sound might occur, especially if they haven't been
diagnosed and have trouble explaining why they're reacting so strongly.
Imagine a person with missophonia living with a friend, but

(02:19):
they don't want to talk because they're bothered by the
sound of their friends breathing. Kumar said, then it gets
a little bit more complicated because they also have this
feeling that other people are not believing them so they
suffer in silence. The researchers studied measurements from functional and
structural magnetic resonance imaging, that is, fMRI and MRI, observing

(02:43):
parts of the brain used for processing perceptions and emotions.
They also monitored physiological data like heart rate and sweat
responses to measure participants stress levels. Participants heard three kinds
of sounds, trigger sounds like eating, breathe, or drinking, unpleasant
sounds like a baby's cry or a person's scream, and

(03:06):
neutral sounds like a busy cafe or the sound of rain.
Both groups were asked to rate how annoying the sounds were.
Those with mesophonia rated how much the sounds triggered mesophonic reactions.
Those without it rated how antisocial the sounds would make
them or how much they would dislike being around the noise.

(03:28):
The group with mesophonia did experience distress typical of their
disorder from the trigger sounds, but the unpleasant sounds didn't
produce the same response. After hearing the trigger sounds, the
group with misophonia experienced increased heart rates in sweating measured
through galvanic skin responses, but also called electrodermal activity. Basically,

(03:49):
when we sweat, our skin becomes more electrically conducive because
water is conducive, so you can measure even small changes
in whether or how much we're sweating by attaching electricrodes
to two fingertips and sending a tiny amount of current
through them. Increases in heart rate and sweat indicate that
we're experiencing stress. According to the authors, these responses indicate

(04:13):
a fight or flight response to the trigger sounds. They
wrote that people with messophonia tend quote to escape from
the environment of trigger sounds or experience anxiety and anger
if unable to escape. The group with missophonia in the
study also exhibited abnormal salience. Salience is how much we

(04:34):
notice something. The trigger sounds stood out more for these participants,
and the parts of their brains involved in processing salience
were more active than was observed in the other participants.
In people with missphonia, the trigger sounds activated the anterior
insular cortex of the brain, a network that directs our
attention towards stimuli that are, for whatever reason, irrelevant or

(04:58):
meaningful to us. Why Normally, this part of the brain
helps us say hear our name, in a noisy room
because we've learned that that's important, or it might draw
our attention to the color red or yellow for evolutionary reasons.
In the participants with missophonia, the trigger sounds also activated
parts of the brain related to processing and regulating emotion.

(05:21):
The researchers also asked all of the participants questions about
body consciousness based on notions of the private body, the
public body, and body competence. Kumar explained that the private
body is basically inner perception, like when a person can
easily sense their heartbeat. The public or outer body references

(05:41):
your consciousness about presenting yourself to and being perceived by others.
Body competence refers to how strong, fast, and coordinated you
feel like you are in comparison to other people. Both
groups had similar scores in body competence, but Kumar said
found that people with misceophonia had a higher score on

(06:02):
the private body and also on the public body, so
they were definitely perceiving their body internally differently compared to
people who don't have missophonia. The researcher's data can't tell
us whether this unusual self perception is a cause of
or a result of missophonia, but Kumar is optimistic that

(06:24):
further research can be directed to basically quiet the brain
structures related to the condition, and he hopes that in
the meanwhile, the fact that research is being done will
bring people a bit of comfort. Today's episode is based
on the article why do some people hate the sound

(06:45):
of chewing? Scientists might have the answer on how stuffworks
dot Com, written by Shelley Dancy. Brain Stuff is production
by Heart Radio in partnership with how stuffworks dot Com
and is produced by Tyler Klang. Four more podcasts my
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