Is there a scientific explanation for dramatic body shaking and trembling in religious settings? (see videos for illustrative examples)

The exhibited behaviours are episodic glossolalia, collapsing, fainting, trembling, jerking, convulsing, contorting, and shaking. The individuals performing these episodic behaviours report experiencing overwhelming emotions of love, peace, ecstasy and euphoria. The exhibited behaviours are inconsistent with the claimed emotions, so perhaps another way to understand the question is to explain why individuals behave in a manner that is inconsistent with their emotions. Examples of behaviour associated with euphoria do not generally include glossolalia, collapsing, fainting, trembling, jerking and shaking. The exhibited behaviours are more congruent with the emotions of stress, anxiety, fear, and confusion.

The exhibited behaviours and reported emotional experiences are observed in both religious and nonreligious settings including:

• Indigenous american indian ghost dance ceremonies,
• Indian Rain Dance to God Parjanya,
• Balinese ceremonies,
• Hindu Kundalini Awakening ceremonies, and
• Fringe martial arts.

The adoption by some Christian sects of the exhibited behaviours, and other behaviours such as laughing and drunkenness, appears to be relatively recent with the "Toronto Blessing" in the 1990s appearing to be significant. In all cases exhibited, the behaviours and emotions appear to occur in the presence of, and behest of, a charismatic and captivating authority figure.

In the absence of peer reviewed literature on the topic, eight strawman hypotheses are proposed. In accordance with the principle of parsimony, the hypothesis without discrediting evidence and the least number of assumptions will be tentatively selected.

The strawman hypotheses identified are:

The behaviours and emotions may result from:

1. an unidentified invisible force (e.g. a spirit or god) causing electro neurological impulses that result in such behaviour,
2. a hysterical state induced by the leader or other Mass psychogenic illness,
3. a hysterical state self-induced by the individual,
4. the individuals are conforming to the directions of an authority figure and/or subject to peer pressure and conforming to the social norms of the group,
5. the individuals suffering from a Functional Neurological Disorder (FND),
6. the individuals being paid actors,
7. the individuals being in a state of hypnosis,
8. the individuals are attention seeking, or
9. a Dissociative disorder.

Each of these strawman hypotheses will be examined in turn:

1. Unidentified invisible force/Divine Intervention. No confirmatory evidence has yet been tendered supporting the existence of invisible forces, other than the four fundamental forces of gravity, electromagnetism and strong and weak nuclear forces. As the exhibited behaviours are widespread across non-intersecting religious and cultural groups, a further unanswered question is which of the unidentified invisible forces is capable of inducing the emotions and behaviours or whether all unidentified invisible forces are equally capable of inducing such emotions and behaviours. The Christian sects shown in the exhibited videos subscribe to their religion by way of faith, which is ordinarily defined as a belief in the absence of supporting evidence. There being no scientific evidence of the involvement of unidentified invisible force(s), this hypothesis is dismissed. For further discussions on divine intervention, see https://doi.org/10.1080/14746700802396106 , https://doi.org/10.5840/faithphil199714215 , https://doi.org/10.31577/orgf.2019.26106 , and https://doi.org/10.7591/9781501735295-074 .

2. Hysterical state induced by the leader: The presence of a charismatic and captivating leader in all the videos provided suggests credence for this option. The causes of Mass Psychological Illness remain speculative. The psychological mechanism capable of inducing a hysterical state are not yet understood and the mechanisms used by the charismatic leader are not uniform between the ghost dance ceremonies, Hindu Kundalini Awakening ceremonies, particular martial arts and Christian sects. There being no identified scientifically established mechanism capable of inducing hysterical states, this hypothesis is dismissed.

3. Hysterical state induced by the individual: No established mechanism by which an individual may self-induce a hysterical state was identified, therefore, this hypothesis is dismissed.

4. Conformance to the social norms: There is strong evidence that individuals seek to conform with the directions of authority figures and social norms. Conformance is due to the desire to avoid behaviours that would exclude them from the group(Burger, 2019; Milgram & Gudehus, 1978; Philippe & Durand, 2011; Schmidt et al., 2019). YouTube records examples of individuals participating in such behaviours but later ceasing the behaviours. These individuals report conforming to the behaviours due to social and situational pressure. It seems inconceivable that individuals who can participate in activities (in some cases for many years) that reliably induce feelings of love, peace, ecstasy and euphoria would ever seek to depart from such behaviours, yet the internet abounds with stories of individuals ceasing to perform such behaviours. The prevalence of individuals reporting conformance to social and situational pressure and the abundance of established peer reviewed literature identifying the basis of socially conforming behaviour suggests that this hypothesis is not immediately dismissable and worthy of more rigorous scientific analysis. References to individuals departing from these behaviours can be found here, here, here, here and here.

5. Functional Neurological Disorder (FND): Individuals suffering FND exhibit behaviours for many years and do not describe the concurrent emotions as love, peace, ecstasy and euphoria. There being no similarity between FND and the relevant behaviours and emotions, this hypothesis is dismissed.

6. Paid actors: Given the number of observed occurrences of the exhibited behaviours, it seems inconceivable that at least one paid actor would not have published their experiences in either paid media or a blog. The absence of individuals claiming to be paid actors discredits this hypothesis and it is therefore dismissed.

7. Hypnosis: Hypnosis is defined as a human condition involving focused attention, reduced peripheral awareness, and an enhanced capacity to respond to suggestion. It is unclear from the exhibited behaviours that the process of hypnosis matches the behavioural expectations of hypnosis (Williamson, 2019; Mayo Clinic) and nor does the hypnotic induction process appear to match those in the exhibited videos. For these reasons, this hypothesis is therefore dismissed.

8. Attention seeking: Attention seeking seems very likely given the nature of the YouTube based individual testimonies. Attention seeking and Conformance to the social norms appear to be related when the individual seeks to draw attention to their conformance to the social norm (see DOI:10.1111/bjso.12196, DOI:10.1353/jip.2021.0002).

9. Dissociative disorder: It seems less likely that anyone with a dissociative disorder would post (or would be able to) post on YouTube.

Of the nine strawman hypotheses, only Conformance to the social norms and Attention seeking avoided immediate dismissal. Both hypotheses that avoided dismissal undoubtedly requires more formal scientific assessment, presumably by way of surveying a substantial number of individuals who have previously participated in such behaviours.

Note: No peer reviewed research was identified in the preparation of this response. All research was therefore restricted to Wikipedia and YouTube (except where specifically identified).

A sample of resources accessed:

https://en.wikipedia.org/wiki/Glossolalia

https://en.wikipedia.org/wiki/Slain_in_the_Spirit

https://en.wikipedia.org/wiki/Kundalini

https://www.recoveringfromreligion.org

https://www.restorationcounselingseattle.com/

https://en.wikipedia.org/wiki/Attention_seeking

https://youtu.be/SwjCuyuKf3s

https://youtu.be/F6c4BxktCdU

https://youtu.be/bZIrU7m0gx0

https://youtu.be/1YTZkHKN6l4

https://youtu.be/kD3g5rg0CqE

https://youtu.be/WaT06FX85G4

https://youtu.be/FEYW2vqqNDQ

https://youtu.be/TUvNW0ZZoDw

https://youtu.be/8L1Fslf3g2M

https://youtu.be/Q5LpMxYfHn4

https://youtu.be/G22hZ81Vku0

https://youtu.be/LDRPOxqVw90

https://www.mayoclinic.org/tests-procedures/hypnosis/about/pac-20394405

References

• Burger, J. M. (2019). 13.3 Conformity and Obedience. Introduction to Psychology. https://openpress.usask.ca/introductiontopsychology/chapter/conformity-and-obedience/

• Milgram, S., & Gudehus, C. (1978). Obedience to authority. Ziff-Davis Publishing Company. https://www1.psych.purdue.edu/~willia55/120/LectureSocialF10.pdf

• Philippe, D., & Durand, R. (2011). The impact of norm-conforming behaviors on firm reputation. Strategic Management Journal, 32(9), 969–993. https://onlinelibrary.wiley.com/doi/abs/10.1002/smj.919

• Schmidt, M. F. H., Rakoczy, H., & Tomasello, M. (2019). Eighteen‐Month‐Old Infants Correct Non‐Conforming Actions by Others. Infancy: The Official Journal of the International Society on Infant Studies, 24(4), 613–635. https://doi.org/10.1111/infa.12292

• Williamson, A. (2019). What is hypnosis and how might it work? Palliative Care: Research and Treatment. https://doi.org/10.1177/1178224219826581

As the OP notes, this has been a difficult topic for Skeptics.SE. I'm going to try to answer here, but over on Skeptics this would probably be labelled as "Original Research".

The problem for Skeptics.SE is that the claim being challenged is that these shaking movements have a supernatural cause. All we can say for certain is that we can't rule out a psychological cause, but psychological or neurophysiological explanations backed by evidence don't seem to be available.

In the absence of a proper evidence-based theory of what is going on here we can only fall back on "mass hysteria", or as its more politely known these days, "mass psychogenic illness" (MPI). However this is really only a label for a bunch of phenomena that we guess are related. There is also the problem that MPI is the diagnosis used when nothing else can be found.

Having said that, Wikipedia quotes the following list of attributes of MPI outbreaks, so we can at least compare this phenomenon with it:

• symptoms that have no plausible organic basis; Yes.

• symptoms that are transient and benign; Yes.

• symptoms with rapid onset and recovery; Yes.

• occurrence in a segregated group; I think this may mean a group segregated for weeks rather than hours. On the other hand some preachers call on their congregations to separate themselves from the sinful world; it would be interesting to score these events against that criterion.

• the presence of extraordinary anxiety; No. However other strong emotions are certainly present, and this might well have the same effect.

• symptoms that are spread via sight, sound or oral communication; All three are present in these services, but that doesn't prove it is how this is spread.

• a spread that moves down the age scale, beginning with older or higher-status people; Unknown, but a review of videos of these events might provide data.

• a preponderance of female participants. Again, the videos might provide data.

The Wikipedia article also lists medical symptoms that occur in MPI. As the OP notes, shaking and fainting is not in the list. However these events are not socially constructed as "illness", so if this is MPI it is not surprising that harmful medical symptoms are not present (although the shaking and falling does bear a resemblance to Parkinson's Disease).

In conclusion, MPI or something like it appears to be the most plausible explanation for this phenomena, and a review of videos of these events might shed further light on this.