Individual differences in sensory sensitivity may explain why only some people experience the complex emotion of ASMR. We define sensory sensitivity as self-reported perceptions of how an individual processes and responds to internal and external sensory cues. This definition refers to subjective sensory sensitivity (i.e., first-person reports) rather than behavioural (i.e., individual differences in the ability to detect and discriminate sensory stimuli) or neural (i.e., the extent of neural activation induced by sensory stimuli) sensory sensitivity (Ward, 2019). Our definition encompasses sensory processing of exteroceptive cues originating externally (e.g., sights and sounds) and interoceptive cues coming from within the body (Craig, 2002).

We propose that the ability to experience ASMR and its resulting intensity may be underlined by heightened sensory sensitivity to exteroceptive and interoceptive cues. We speculate that (stronger) ASMR is underlined by at least two component processes involved in the translation of external input to subjective feelings:

(1) heightened sensory sensitivity to external cues involving greater salience to ASMR triggers (which may therefore be difficult to disengage from) and

(2) enhanced interoceptive awareness involving the translation of sensory stimuli to stronger internal emotional responses (enhancing the intensity of emotional responses to ASMR triggers).

The proposal that these component processes underline the presence and intensity of ASMR is based on research (reviewed below) on the related phenomena of aesthetic emotions and misophonia, which are likely to have similar underlying mechanisms to ASMR.

Like ASMR, the experience of complex emotional states known as aesthetic emotions (e.g., awe, elevation, frisson) are not universal and vary in intensity between people. For example, not everyone experiences frisson (a tingling sensation on the back of the head resulting in goosebumps) (Grewe et al., 2011) or the tingling sensations associated with elevation (Haidt, 2003) or feeling moved (Menninghaus et al., 2015). Although ASMR is qualitatively different to other aesthetic emotions, they are related and may have similar underlying determinants. Frisson and ASMR are significantly positively correlated, (Kovacevich and Huron, 2019, Roberts et al., 2019), they show similar neural activation patterns (Lochte et al., 2018), and 87% of ASMR respondents reported experiencing frisson (Fredborg et al., 2017).

Individual differences in complex emotional states may reflect neurodevelopmental differences in how sensory input is translated into subjective emotional responses. For instance, those who experience more intense emotional responses to music have stronger white matter connectivity between neural regions involved in sensory and emotional processing (Sachs et al., 2016), suggesting that individual differences in the way that people experience emotion as a result of external sensory stimuli (e.g., music) may reflect differences in the structural organisation of the brain. ASMR may also be associated with comparable neural differences in how sensory input and emotional experience are integrated. People with ASMR show reduced functional connectivity within the Default Mode Network (a constellation of brain regions involved in self-referential processing; Poerio et al., 2018), but increased functional connectivity between the DMN and clusters in executive-control and visual resting state networks (Smith et al., 2017). This has led to the suggestion that ASMR is driven by an inability to inhibit sensory-emotional responses.

Individual differences in interoception (internal sensory sensitivity) are also important for aesthetic emotions. Tingling (e.g., chills, goose-tingles) is a prototypical feature of aesthetic emotions (Menninghaus et al., 2019) and is the canonical feature of ASMR (where tingling is located primarily on the head). Tingling can be conceptualised as spontaneous and sub-conscious afferent signals from neurons at the skin being brought to conscious awareness via interoceptive attention (see Tihanyi et al., 2018). Individuals who are more sensitive to interoceptive cues experience more frequent ‘spontaneous’ tingling sensations with greater intensity (Michael et al., 2015, Tihanyi and Köteles, 2017). Individual differences in interoception also explain variation in subjective emotional experience. People who are more sensitive to interoceptive cues experience emotions more intensely (Wiens et al., 2000) and place greater emphasis on information from the arousal component of core affect (Feldman-Barrett et al., 2004).

Misophonia is a condition describing aversive and angry feelings in response to certain sounds (e.g., tapping, chewing, lip smacking, and pen clicking) (Wu et al., 2014). Although one might expect ASMR and misophonia to be negatively associated because similar triggers produce opposite emotional reactions, research shows that they commonly co-occur. ASMR-sensitive individuals have elevated levels of misophonia (McErlean & Banissy, 2018), just under half of ASMR participants (43%) experience misophonia (Barratt et al., 2017), and 49% of misophonics experience ASMR (Rouw & Erfanian, 2018). One explanation for the unlikely co-occurrence of ASMR and misophonia is that they share a common mechanism, both being underpinned by an increased sensitivity to external sensory stimuli, particularly sound. Contextual factors and associated emotional appraisal processes might then determine whether the same stimulus (e.g., eating sounds) is evaluated as positive or negative by the same individual (Samermit et al., 2019).

A range of studies provide evidence that misophonia may be underlined by heightened sensory sensitivity. Correlational evidence shows that misophonia is positively associated with the severity of sound sensitivity, external sensory sensitivity more generally, and internal body awareness (McKay et al., 2018, Wu et al., 2014, Zhou et al., 2017). Research on the neural basis of misophonia also indicates that the condition is driven by altered sensory sensitivity (Kumar et al., 2017). Misophonics show hyperactivity of the anterior insular cortex when exposed to trigger sounds (e.g., eating, breathing), a key region involved in interoception and emotion processing (Gu et al., 2013). Misophonics also score higher on subjective interoceptive awareness suggesting that they may be better able to decipher internal bodily states. Whether or not similar processes are at play during ASMR is an open question, but the association between the two phenomena points to potentially shared mechanism of heightened sensory external and internal sensitivity, which deserves further investigation. In the present study, we examine for the first time the relationships between ASMR and interoceptive awareness, body awareness, and sensitivity to exteroceptive cues.

Although not a form of sensory sensitivity itself, trait mindfulness is also relevant to ASMR and sensory sensitivity. Mindfulness describes the tendency to apply cognitive thought processes to enhance the awareness and acceptance of ones’ present phenomenological experience, including internal and external sensory input (Gibson, 2019). The ‘awareness’ component can be thought of as a meta-sensory sensitivity – the ability to direct attention towards sensory information. The ‘acceptance’ component relates to the downregulation of over-reactive cognitive and behavioural responses to sensory stimuli (Gibson, 2019). Indeed, the ‘awareness’ component is positively correlated with interoception measures (Hanley et al., 2017), whereas the ‘acceptance’ component is negatively correlated with behavioural measures of sensory sensitivity (Takahashi et al., 2019).

With respect to ASMR, ASMR-sensitive individuals typically score higher than controls on global aspects of mindfulness (Fredborg et al., 2018). In particular, they have higher rates of mindful awareness compared to controls, a feature which also predicts an increased reported frequency of ASMR and aesthetic chill experiences (Del Campo, 2019). This latter finding echoes research that aesthetic chills are positively associated with mindful awareness but negatively associated with mindful acceptance (e.g., non-judging; Harrison & Clark, 2016). Here, we test whether this observation also applies to ASMR and extend previous research (Fredborg et al., 2018) by employing a measure of mindfulness (the Five-Factor Mindfulness Questionnaire, FFMQ; Baer et al., 2008) which separates out awareness and acceptance aspects of the construct.

The research reviewed above provides theoretical support for our proposal that ASMR may be underlined by heightened sensory sensitivity to exteroceptive and interoceptive cues. In this study, we sought to provide more direct empirical evidence for our proposal using both:

(1) A correlational approach examining the extent to which individual differences in sensory sensitivity measures can explain variability in ASMR intensity.

(2) A categorical approach examining whether there are substantial differences in sensory sensitivity between people who are able to experience ASMR and those who are not.

Given that sensory sensitivity is a multifaceted construct with different but overlapping conceptualisations depending on the area of study (Ward, 2019), we took a broad approach by measuring individual differences in sensory sensitivity using six different but complementary measures encompassing sensitivity to interoceptive and exteroceptive cues, affective and behavioural self-report measures, and mindfulness.