In over a decade of its existence—since 2012, to be exact—the ‘Mildly Annoying’ community has covered nearly every and any annoying situation there is. They might seem like minor inconveniences to some, but they can get on people’s nerves nevertheless. Moreover, what doesn't seem the slightest bit frustrating to some might make others’ blood boil.

“There are many individual differences in what presses our buttons enough to annoy us,” a neuroscientist and senior lecturer at Rensselaer Polytechnic Institute, Alicia Walf, told Bored Panda in a recent interview. “In general, annoyances are unpleasant stimuli that are unpredictable and uncontrollable and persist for some time. There is context-dependency on what annoys us as well, making annoyance a volatile and hard to anticipate emotion.

“Unlike anger, in which the same things or situations are likely to produce it time and again, the same thing can be simply unpleasant one day, but then be extremely annoying the next.”

“It is perplexing when seemingly insignificant things produce annoyance in us,” Dr. Walf pointed out. “As a general rule, we focus on the bad. Given the limited attention we have to process everything going on inside us and in our complex and dynamic environments, our brain’s default is to focus on what might be harmful or even out of place, a mistake that we frustratingly cannot fix.

“When we are stressed, our attention is quickly refocused on what is causing the stress because it may be something that can seriously harm us. It might be a similar process for annoyance. We can’t help but notice that thing that is unpleasant so we focus our attention on it. Annoyance can come from this because we cannot change the situation and we do not see an end in sight.”

Prof. Walf emphasized that it’s difficult to predict what annoys most people and why, but there are ideas of potential reasons for these individual differences. “Some of it may be due to personality—some people are more prone to react with negative emotions like anger and annoyance. Some of it may be due to present emotional states; for example, individuals feeling irritable (maybe because of lack of sleep) are more prone to annoyance.”

“Another major contributor is stress,” the neuroscientist continued. “Stress refocuses our attention on our environment, which may include something annoying. With stress, the modulation of the limbic and threat regions by the frontal cortex breaks down and our reactions are more driven by the threat and limbic systems than by the higher-level cognitive processing of the frontal cortex.

“Given that there is a relationship between stress and annoyance, feeling annoyed at even minor things might be due to greater activation in these threat and limbic regions without this oversight from the frontal cortex that is typical. Just as much as stress can amplify annoyances, studies have shown that exposure to annoyances also causes stress.”

It’s arguably safe to say that we all have pet peeves, and they seemingly get even more bothersome when we’re already stressed. Survey Monkey revealed what are some of the most common pet peeves when it comes to sharing a home and working in the office. The most annoying thing in the former environment is leaving common spaces messy, with as much as 63% believing so. Others include not taking out the trash, talking loudly on the phone, or taking food without permission with 45%, 30%, and 24% respectively admitting to being aggravated by such situations.

When it comes to work, people are seemingly most annoyed about colleagues complaining about their work or fellow co-workers (53%). It is followed closely by managers who don’t give credit where credit is due (50%), colleagues who are late to meetings (33%) or who fail to recognize your contributions (31%).

Loud chewers and sources of similar sounds are also among popular pet peeves that could drive a person completely nuts. Someone enjoying their sandwich with intense lip smacking or repetitive clacking of the tongue is as close to torture as one gets to certain people. Especially those with misophonia—a disorder which entails having a decreased tolerance to certain sounds and sensations related to them.

According to researchers from King’s College London and University of Oxford, nearly one-fifth—18.4% to be exact—of people in the UK find everyday sounds, such as chewing or loud sniffing, difficult to bear.

NPR correspondent Joe Palca pointed out that in order for things to be annoying they have to tick three boxes: they have to be unpleasant without being physically harming, unpredictable and intermittent, and persist for an uncertain period of time. All of these combined ought to make whatever ticks the boxes quite aggravating for sure. (It’s pretty safe to say that a loud chewer sitting at a nearby table would checkmark them all.)

Joe Palca also emphasized that there is no universal theory when it comes to annoyance, as the things that irritate people vary from person to person; they are also so oddly specific, there can be a million different ones.

Some of the correspondent’s personal favorite ones, which he revealed to the American Psychological Association, included people getting annoyed by someone picking lint off their clothes and people not counting the change into a person’s palm.

Whether it’s someone’s loud breathing or a picture of tiles so uneven, they must be destroyed, pet peeves and similar annoyances can have a negative effect on a person. They typically cause negative emotions or even stress, which is known to have an adverse effect on one’s physical and mental health.

Healthline pointed out that stress can activate the “fight or flight” response in one’s body and cause numerous problems, such as headaches, heartburn, high blood pressure, weakened immune system, insomnia, and others.