Discussion
Examining the largest sample of misophonia participants to date, the aim of this study was to investigate the relationship between misophonia and mimicry. More specifically, three questions were addressed: (i) relationship between the likelihood to mimic as a function of misophonia severity, (ii) whether the act of mimicking was related to a particular set of trigger sound categories (as defined by the MQ (Wu et al., 2014)), and (iii) what benefits, if any, mimicking provided to people with misophonia (identified through the IMQ).
Our results show that mimicry is widely prevalent in misophonia and that its likelihood increases with greater misophonia severity. This finding is consistent with results from a recent neuroimaging study from our group (Kumar et al, 2021), which for the first time hypothesized the role of ‘mirroring’ the action, and not the sounds per se, as the primary driving factor in misophonia. The neuroimaging study, by showing stronger resting state connectivity between auditory and visual cortex and the pre-motor area of the brain in misophonia, argued that watching or hearing action sounds (e.g., orofacial movement for eating/ chewing sounds) of the trigger-person results in driving the same part of the motor cortex that is involved in generating the perceived action. The current study, based on self-reported measures of how people with misophonia respond to and cope with triggers in daily life, provides support to the ‘hyper-mirroring’ hypothesis of misophonia.
The phenomenon of mimicry is ubiquitous in social interactions and has been a well-researched topic in social psychology and neuroscience (Prochazkova and Kret, 2017; Arnold and Winkielman, 2020; Palagi et al., 2020). Mimicry can be broadly divided into two categories: intentional and spontaneous. Intentional mimicry (sometimes also called imitation or emulation) involves explicit intention to copy and reproduce somebody else’s actions. In a misophonia context, this would be the case when a person with misophonia, on seeing/hearing the actions (e.g., orofacial movement for eating/chewing sounds) of the trigger-person, deliberately repeats the observed action. Spontaneous mimicry, on the other hand, is the automatic reproduction of another individual’s motor movements, behaviour, or facial expression without explicit intention or awareness to do so. For example, in a seminal study (Chartrand and Bargh, 1999) demonstrating spontaneous mimicry, a confederate manipulated her actions while interacting with participants: in different sessions, she either touched her face or shook her leg while both the confederate and participants were involved in an irrelevant task of describing pictures to each other. Analysis of video recording of the interaction showed that participants touched their face more in the presence of a face-touching confederate and wiggled their foot more in the presence of a foot-shaking confederate. Debriefing after the experiment showed that participants did not notice any ‘odd’ behaviour of the confederate and were not aware of their mimicking of the actions of the confederate implying that reproduction of the actions was implicit and unintentional. With respect to misophonia, spontaneous mimicry would occur if mere observation or listening to the trigger sounds of action automatically elicits a corresponding action (e.g., orofacial movements for eating/chewing sounds) in a person with misophonia with them not knowing anything about it. Although not within the misophonia context, spontaneous mimicry has been shown in the domain of eating behaviour: people are more likely to take a bite of food or sip of a drink when their companion does so (Larsen et al., 2010; Hermans et al., 2012; Bell et al., 2019). Even the sounds of eating alone can elicit eating mimicry in the listener (Zin et al., 2015).
How does misophonia relate to mimicry? The basic premise of our argument is that misophonia is a result of increased spontaneous mimicry in response to the actions (e.g., orofacial movement) of the trigger-person that produce trigger sounds (e.g., eating/chewing sounds). The excessive spontaneous mimicry, which possibly arises due to the failure of contextual modulation (either amplified in excess or not suppressed enough by the contextual/situational settings) is then perceived as inappropriate in terms of interfering in a person’s current goals and actions. This strong drive, initiated by an external source, to repeat the actions can be felt as violating or invading personal space or can lead to a sense of loss of self-control. This is consistent with people with misophonia describing their experience of trigger sounds as ‘invasive’, ‘intrusive’, ‘insulting’, ‘violating’ and ‘offensive’ (Rouw and Erfanian, 2018). There is also evidence that trigger sounds are perceived as interfering in one’s current goals. In a study using a Stroop task, Daniels et al (2020) showed that people with misophonia are impaired in maintaining the current goals of the task specifically in the presence of trigger sounds. Since perceived interference, particularly when it is attributed to another social agent, can be a cause of anger (Izard, 1991), this also explains why anger, and in extreme cases, aggression could be a dominating emotional response in misophonia. One possible way to counter the covert drive for spontaneous mimicry is to overtly mimic the action of the trigger-person (e.g., orofacial movements in response to sounds of eating/chewing). The overt mimicry, in contrast to implicit and unintentional spontaneous mimicry, is intentional and done voluntarily as a coping mechanism to ‘cancel out’ the trigger sound. The reason why overt mimicry in misophonia can ‘dampen’ the response to the external trigger is that self-executed movement alone (with or without any sound generation, e.g. orofacial movement) done in synchrony with external movements can lead to predictions about the upcoming stimulus, much like an efference copy or corollary discharge making a prediction of the sensory consequences of self-generated actions (Blakemore et al., 2000), which is then compared with the actual stimulus and the discrepancy between the two (prediction error) is processed further. The amount of dampening of the trigger stimulus would depend on how accurately the self-action can predict the stimulus: the higher the accuracy of prediction, the lower the prediction error and thus the greater the relief provided by the overt mimicry. Moreover, the overt mimicry can provide an increased sense of self-control: rather than being a ‘passive’ recipient of the excessive drive to spontaneously mimic the actions of the trigger-person, the person with misophonia can now do the same action which is under their control. This is in agreement with subjective reports of several people with misophonia who describe their act of deliberate mimicking as a means of ‘gaining control over the situation’ (as told to the senior author in personal communication/discussion).
Our data show that the probability of mimicking increases with misophonia severity (Figure 1). When asked about the type of mimicry, 50.5 % (sum of ‘sometimes’, ‘often’ and ‘always’, Figure 4(i)) described their mimicry to be spontaneous and out of their control. About 80% (Figure 4(ii)) of people who reported mimicking, described their act as deliberate and voluntarily driven. As predicted by our model, intentional mimicry provides relief (reported by 68%, Figure 4(iii)) and makes the person feel under control (60.4 %, Figure 4(iv)).
Analysis using multivariable logistic regression showed that, out of all the different types of sound categories examined, sensitivity to eating sounds was the strongest predictor of mimicry (Table 1 and Figure 2). Multivariate analysis using PCA showed that eating/nasal/throat sounds and mimicry loaded onto the same component with high positive loadings implying a positive association between the component and these variables. The eating/nasal/throat sounds are orofacial (face/mouth) sounds involving movement of orofacial muscles and these sounds happen to be the dominant trigger sounds in misophonia (Schröder et al., 2013; Kumar et al., 2014; Jager et al., 2020). We understand there are trigger sounds which are of non-orofacial origins (Hansen et al., 2021) such as pen clicking, keyboard typing, and other environmental sounds. Although the questionnaire did not have mention of these specific sounds, it did include ‘environmental sounds’ as one of the categories and no mimicking effect was observed using either logistic regression or PCA. However, this category is very broad and whether mimicking is restricted to a specific example of this category needs further investigation. The questionnaire also contained a ‘repetitive tapping sound’ which is the closest possible to clicking pen/keyboard typing but no mimicking effect was observed. Although we did not find evidence of mimicking for non-orofacial sounds, the question remains open. One explanation is likely due to the under-representation of triggers of non-orofacial origin in the current sample size given the high prevalence of orofacial sounds as triggers. This would require a further study which balances representation of different trigger types in the sample. Interestingly, logistic regression analysis also showed consonant/vowel sounds significantly correlated with mimicry. Whether these sounds trigger reaction because of the speech/linguistic content or because these sounds are mouth sounds is not clear and their relation to mimicry needs further investigation.
What is the brain mechanism of excessive spontaneous mirroring in misophonia? There is evidence that a ‘mirror neuron system’ (MNS) which contains ‘mirror-neurons’ may underly mimicry in humans (Buccino et al., 2001; Rizzolatti and Craighero, 2004). Mirror neurons fire not only when the subject executes an action but also when the subject sees or hears the action performed by another individual, thereby creating a ‘perception-action’ link. In our recent study (Kumar et al., 2021), based on the findings of stronger coupling between auditory (and visual) cortex and orofacial motor cortex in people with misophonia, we argued for ‘hyper-mirroring’ as the basis of misophonia. This means that the perception of seeing or hearing another individual producing eating/chewing sounds is ‘mirrored’ in the orofacial motor cortex to a greater degree in people with misophonia compared to control participants. This hyper-mirroring then reproduces the action which manifests as (spontaneous) mimicry. Our brain model of ‘hyper-mirroring’ and prevalence of spontaneous mimicry in the current work are therefore consistent with each other.