Speculations on How Misophonia Arises
One issue the jaw dysfunction hypothesis (JDH) has to address is how misophonia arises. Firstly, it requires that significant, or at least perceptible, jaw dysfunction occurs before the development of misophonia. In my case this seems plausible: I think I’ve always had a small jaw. I have a vivid memory of walking down Hessle Road as a child and my dad telling me to keep my chin up and look straight ahead, so I could see where I was going. I must have been 4 or 5. He had a point, but I now wonder whether I was keeping my head in a downward posture because I wasn’t getting the right signals from my mouth to keep it level.
Secondly, it’s interesting to note that I always had an underdeveloped jaw, but that I only started consciously associating it with misophonia when my wisdom teeth started emerging and pushing everything forward. That’s when it became a trigger. Before then, I’d been quite satisfied with how my mouth felt physically and somewhat less satisfied, but not overly distressed about, how it chimed with my self-image. (I’d always thought my head looked weird when looked at from the side, for example in changing room mirrors.)
For the JDH to be true, then, jaw underdevelopment must be necessary for the development of misophonia, and for self-triggered misokinesia (STM) specifically, but not sufficient for STM. It remains an open question why my STM arose only when my wisdom teeth emerged, but one possibility is that this was when the most clinically significant aspects of my jaw dysfunction arose. I believe these are a) narrowness and b) the fact that my lower jaw is trapped behind my upper jaw. (This happened because the forward movement was asymmetrical between jaws: in my lower jaw there was less slack left by missing teeth to take up before things had to start crowding forward.)
Misophonia is a high-level psycho-neurological phenomenon. What I mean by this is that it involves, as well as raw affect and arousal, higher-level mental processes such as social cognition. Whether something is a trigger sound (or image, etc) can depend on context and perceived origin, as well as the raw quality of the stimulus.
This is important because it means that the connection to jaw dysfunction, if there is one, will be similarly multi-level and nuanced. I’m kind of making this up as I go along at the moment (in case you couldn’t tell) because there are many moving parts and observations to take into account.
Given that we’re aware of these two observations about misophonia—that it involves both low-level stimuli and high-level cognition—it seems to make sense to deal with each of them in turn in relation to the JDH. (The involvement of lower-level phenomena can be assumed, based on recent research on e.g. mirroring, without accepting the JDH.)
The Constructed Emotion Theory
My thinking about emotions is heavily influenced by the theory of constructed emotion proposed by Lisa Feldman Barrett in her book How Emotions Are Made. See The Constructed Emotion Theory for more details. The main relevant aspect for this post is the idea that emotions are constructed out of lower-level components depending on context and individual history and personality. The same basic, low-level ingredients can produce one emotion (high-level) in one context and a completely different emotion in another.
Low-Level
What I think I’m proposing at the low level is that jaw dysfunction affects an image that the brain maintains to represent the body, more specifically its ability to perform dynamic movements. This is not a conscious phenomenon, but is used to inform background emotional factors such as how physically flexible and agile you feel. It’s also used directly for things like balance and dexterity in every day actions.
It’s hard to get this across to someone whose jaws are working well, but their proper functioning is important for the very basic bodily functions like moving, breathing, and eating. For example, I can throw a high kick comfortably with my right leg. But the other way, it feels like my right hip can’t provide the necessary support and flexibility to allow my body to turn smoothly through the motion. It makes both my teeth and my hip joint feel like they’re grinding against themselves. The image I’m talking about, very broadly—the one that tracks your agility, etc—is taking this fact into account. The result is the sensation that you’re just not functioning optimally; that your joints don’t meet at quite the right angles, or something.
Think about the fine motor control and precise timing necessary to do something as “simple” as running without sustaining impact injuries or just tripping over yourself. Abilities like this depend on an extremely finely-tuned system of balance, and the way the teeth and jaws fit together is a centrally important piece of that system. I sometimes think of it as being like a reference point—if it’s incorrectly set up, according to the brain’s innate expectations about how the body will be configured and what signals it will receive in which situations, then everything else will be out of whack as well.
This is all to say that the jaws are an integral part of the function of the entire body, at a fundamental level. In terms of constructed emotion, then, jaw dysfunction affects the raw affect and arousal factors by signalling to the brain that the body is somehow trapped or hampered. The way I visualise it is that there’s some kind of abstract, multidimensional representation of the body created by the brain’s predictions (which are in turn informed by memories and sense data) about how the body works. In jaw dysfunction, this representation gets something like a big kink or pinch in it, like if you’d sewn two random parts of a jumper together so that you couldn’t move properly while wearing it. The multidimensionality of the representation—it’s something like “does my body have its full range of motion over time?”—allows for the subtle and dynamic effects of jaw dysfunction to make themselves known in it*.
* Another analogy that captures how I think jaw underdevelopment affects fluid movement is how it feels to walk around in a pair of shoes that’s too small. It’s not just the feet that hurt; the whole musculoskeletal system is thrown out. Tendons get tight, nerves get trapped, etc. I also think the fact that the rest of the body is growing around the jaws, while the jaws are remaining too small and thereby exerting a pulling or pinching effect on the surrounding skeleton – like a tree that’s grown with a jubilee clip around its trunk – might be key to an intuitive understanding of the effect.
In any case, jaw dysfunction has an outsized impact on our ability to execute smooth dynamic movements, so from that point of view a “trapped” or “constricted” type of sensation—perhaps via “misconfigured”—is appropriate. I believe this sensation could be the main qualitative component—in combination with negative affect—from which our brain constructs instances of rage and panic in response to a keen awareness of our jaw configuration. Why this keen awareness only occurs in response to trigger stimuli is another question. One possible answer to this question is that when we’re in control of the action ourselves, that sense of control constantly grounds any potential for a feeling of being taken over by a stimulus, which seems to be common in misophonia. As the brain performs actions, it is constantly predicting their effects, so actions that have negative effects are either prevented altogether, or the edge is taken off by way of a sense of control and a lack of surprise.
Mirroring
It’s known that the brain “mirrors” certain bodily actions: there are neurons that fire both when we perform a certain action, and when we see another person perform that action.
The 2021 research paper on mirroring in misophonia suggested that misophonic responses are the result of a kind of hyper-mirroring, where the external stimulus causes such a strong mirroring response that we actually feel it in our own body. Those researchers also noted the involvement of orofacial motor neurons specifically, supporting the general idea that there’s some special connection between misophonia and the jaws.
So the general hypothesis for how jaw dysfunction causes misophonia is that the external stimuli, via hyper-mirroring, cause us to be acutely aware of our jaw dysfunction.
Even at the low level, then, I would suggest that there may be two distinct elements to the process that eventually becomes a misophonic reaction:
First, we “feel” the stimulus as though it’s coming from inside our own body, which is inherently irritating—it’s a deep violation of personal space and bodily autonomy.
Second, the stimulus “keys into” our brain image representing our orofacial complex and its dysfunction, making us intensely aware of it.
In fact, I don’t know what order these should be in—because mirroring is normal, could it be that it’s the dysfunction that prompts the hyper-mirroring—perhaps by virtue of negative bodily sensations having higher salience—and only then does the stimulus reach the threshold of actually being felt inside the body, as opposed to whatever normal mirroring feels like?
High-Level
The appropriate response to being trapped or constricted for a long time is anger or panic. At the low level, before an emotion is constructed, these are the same: negative affect and high arousal combined with a negative prediction about the body’s ability to move freely, and thereby protect itself and obtain resources.
Once the raw ingredients of rage or panic are in place, our brain senses them and we start to try to figure out where they’re coming from and what the appropriate response is. We already “know” that the evolutionarily correct response is either rage or panic, due to the severity of the affect and arousal factors—those always mean that we either have to get away from something, break out of something, or phsyically overpower something.
It’s interesting to observe here that it’s not really clear which response is appropriate, because really neither of them are: we’re not under attack, or trapped, etc. So in a way our brain doesn’t have much to go on when deciding between rage or panic, and in constructing a coherent emotion with a particular flavour.
I suspect these aspects of the experience will be largely driven by personality, incidental factors in the individual’s history, and context. For me, the flavour of the experience seems to draw from themes of incompetence and “goofy-ness”. I’m not sure what the significance of this is—perhaps none—but I wonder if it could be coming from a general aversion to markers of poor health, of which visibly apparent jaw dysfunction certainly is one.
These high-level aspects of the experience are highly individual and can vary over time.
Changing Triggers
Another major point for the JDH to account for is the fact that the triggers themselves can change over time.
An idea I’ve tried out from time to time is that of a rapidly escalating feedback loop within the brain. I don’t know if it’s the right way of thinking about the process from a scientific point of view, but I do have a sense that the process of generating a full-fledged misophonic response may require some kind of mutual interaction between multiple elements–possibly traversing higher/lower levels of cognition—and may be stronger the more these elements reinforce each other.
Roughly speaking, the elements might be broken down something like this:
The raw stimulus, which causes hyper-mirroring by virtue of negative salience associated with our internal bodily representations signalling jaw disharmony.
The mind feeling the perceived violation of hyper-mirroring—it feels like the stimulus has physically touched us deep inside our body—and therefore hyper-focusing on and possibly replaying the original stimulus and consequent orofacial sensations.
General reinforcement by consistent association of a particular stimulus in a particular context with a misophonic response.
Each one of these factors could cause our triggers to change or fluctuate in intensity over time. Hyper-mirroring seems likely to be affected by how well a stimulus maps to our own body, which in my case seems likely to have been affected by the changing physical positions of my teeth. How much we focus on the perceived violation depends on our mood and other background factors. Finally, general reinforcement is subject to the occurrence of trigger images over time: if we’re subject to a trigger frequently over a short period, we’re likely to develop a habitual response to it that temporarily increases its intensity.
Development
An idea that I think might be relevant to misophonia, and specifically how it can arise from jaw dysfunction, is that of salience. Images in the brain generally have high salience if they’re determined to be of importance to bodily integrity (broadly, homeostasis).
I’ve already outlined a rough idea of how I think jaw dysfunction and its downstream effects could be represented in the brain, as negative qualities of whatever image our brain uses to represent the body in order to serve the predictions and calculations involved in fluid movement.
I think part of why we don’t immediately recognise misophonia as being to do with the jaws, and why we sometimes don’t recognise jaw dysfunction in ourselves, could be that jaw harmony is so fundamental. Recall the idea of it being a “reference point”. Maybe we compensate for it instead—I know I have had a habit of keeping my head in a non-optimal forward position in order to keep my teeth where it feels like they should be, and to make room for my tongue and make breathing easier.
So I think jaw dysfunction might be salient but covert, in that we don’t necessarily consciously associate its affect on our internal body representation with the jaws themselves. The dysfunction is felt more globally. I don’t quite know how to parse all this out. I think jaw dysfunction might be one of those things in medicine that is inherently hard to pin down, because it affects so many systems and there’s so many layers to it—conscious and subconscious effects, conscious and unconscious compensatory actions, etc.
My vague hunch about how jaw dysfunction causes misophonia to develop during childhood is that the brain is tracking a pervasive disharmony in the orofacial and vestibular system. We don’t quite know how to think about it, and because our teeth and jaws are used as a reference point we don’t necessarily identify them as the source of the problem. But there is some basic subconscious feeling of wrongness about the jaws.
Then, when we hear or see things that correspond to our jaws—which includes hearing mouth sounds and seeing people eating—we mirror them. With healthy jaws, this mirroring would go unnoticed. But since something about our jaws is wrong and therefore has salience, we direct more than the usual amount of attention to the trigger and to our corresponding orofacial mirroring sensations.
Over time, I believe that these two things—a vague sense of dysfunction resulting in a feeling of constrictedness; and consequent increased attention paid to mirroring—could create the conditions for misophonic sensitivity. I believe the increased functional connectivity identified in The Brain Basis for Misophonia could be a downstream effect of this, as opposed to being the ultimate cause of misophonia. Neurons that fire together wire together, and pathways become stronger the more they’re activated.