Somatosensory illusions elicited by sham electromagnetic field exposure, 2020, Wolters et al

[Andy]

Objective
According to the predictive processing theory of somatic symptom generation, body sensations are determined by somatosensory input and central nervous predictions about this input. We examined how expectations shape predictions and consequently bodily perceptions in a task eliciting illusory sensations as laboratory analogue of medically unexplained symptoms.

Methods
Using the framework of signal detection theory, the influence of sham Wi-Fi on (i) response bias (c) and (ii) somatosensory sensitivity (d’) for tactile stimuli was examined using the somatic signal detection task (SSDT). A healthy student sample (n = 83) completed the SSDT twice (sham Wi-Fi on/off) in a randomized order after watching a film that promoted adverse health effects of electromagnetic fields (EMF).

Results
When expecting a Wi-Fi signal to be present, participants showed a significantly more liberal response bias c (p = .010, ηp2 = .08) for tactile stimuli in the SSDT as evidence of a higher propensity to experience somatosensory illusions. No significant alteration of somatosensory sensitivity d’ (p = .76, ηp2 < .002) was observed.

Conclusions
Negative expectations about the harmfulness of EMF may foster the occurrence of illusory symptom perceptions via alterations in the somatosensory decision criterion. The findings are in line with central tenets of the predictive processing account of somatic symptom generation. This account proposes a decoupling of percept and somatosensory input so that perception becomes increasingly dependent on predictions. This biased perception is regarded as a risk factor for somatic symptom disorders.

Paywall, https://journals.lww.com/psychosoma...sensory_illusions_elicited_by_sham.98487.aspx
Sci hub, no access.

 

[spinoza577]

...body sensations are determined by somatosensory input and central nervous predictions about this input.

It´s metaphoric usage of "predictions", better would be "processing" . Also "interpretation" is metaphoric, and almost as potentially misleading as "prediction".

Negative expectations about the harmfulness of EMF may foster the occurrence of illusory symptom perceptions

Non-metaphoric usages suddenly.

Researchers, you miss completely the logical possibility that in the machinery of the CNS something could be unbalanced, resulting in diseases. Thanks again for this instructive short cut. Let me guess, your empirical result says nothing about persisting diseases. Would have been honest to have something like this mentioned.

 

[Jonathan Edwards]

I have only looked at the abstract but this seems to be the same muddle as coming the UK people talking about predictive models. My understanding is that predictive models do not relate to their proposal at all. The predictive model says that we experience the discrepancy from the prediction or we take input to confirm the prediction. If the prediction was too 'strong' then reality would seem surprisingly 'weak' - i.e. the innocuous nature of stimuli would become salient.

At least that is how I understand it.

 

[rvallee]

So it sounds like the SSDT, whatever it is, is not a reliable tool, then. But I guess that's unthinkable. Real scientists will spend months, years, tuning and calibrating their instruments to make sure they are reliably measuring exactly what they intend to measure. But these jerks and their awful questionnaires? They can't even imagine the possibility that its responses may not be reliable.

Weird idea to remove all common sense and rational thinking but it does provide for unlimited employment opportunities, it seems.

 

[James Morris-Lent]

To me this sort of 'nocebo' research sinks itself. If they actually thought that this video changed subject's beliefs and left them susceptible to deleterious effects, this study would be unethical. So (hopefully) they must not think so. So that means that they think the observed effects are unimportant transient suggestibility which would be meaningless in the context of trying to understand chronic debilitating conditions.

This goes against the 'unhelpful beliefs' - or maybe 'unhelpful expectations' is better in this case - model, as it then simply goes to illustrate how trivially easy it is to elicit subjective changes in unblinded circumstances simply due to suggestibility. (The test is not a questionnaire but it is certainly subjective and highly open to suggestibility bias.) Which of course runs counter to the whole evidence base behind 'psychosomatic' diagnosis and treatment of FND or whatever other terminology.

Maybe I am not quite on to what they think their logic is but at best this seems inconsequential to anybody trying to prove anything positive about how disease is 'psychosomatic'.