Categorical Interoception Project: How generalization and classification strategies link anxiety and interoception

Project Information

CIP

Grant agreement ID: 653750

DOI

10.3030/653750

Project closed

EC signature date 5 May 2015

Start date 1 April 2016

End date 31 March 2018

Funded under

• EXCELLENT SCIENCE - Marie Skłodowska-Curie Actions

Total cost

€ 172 800,00

EU contribution

€ 172 800,00

Coordinated by

UNIVERSITE DU LUXEMBOURG
Luxembourg

Periodic Reporting for period 1 - CIP (Categorical Interoception Project: How generalization and classification strategies link anxiety and interoception)

Reporting period: 2016-04-01 to 2018-03-31

Summary of the context and overall objectives of the project

Nothing is closer to us than our body, but few things are as elusive as the perception of bodily sensations. Research and general medical practice provide ample evidence that there is often a (seemingly) puzzling disconnect between sensation individuals report and physiological processes measured by diagnostic means. Correlations between self-reported bodily sensations and physiological changes are usually low in healthy individuals and patients with a somatic disease. Research consistently reports that negative affect is related to stronger nocebo effects, higher levels of symptom report and catastrophizing interpretations. Inadequate perception and interpretation of bodily sensations impacts coping behaviour and, in the long term, physical health and mental well-being.
This project tested whether categorisation, as a fundamental perceptual process, links anxiety and interoception via the choice of perceptual decision strategies and via processes of within-category generalisation. We suggest that in somatic decision-making, the brain continuously bundles the flow of interoceptive information into distinct categories such as “pain” or “pleasure”. By assigning sensations to interoceptive categories, it is possible to infer hidden information about causes and consequences and apply coping schemata fast and efficiently. If we know, for example, that we suffer from an allergy and not from a cold, we can infer causes and consequences, take measures to reduce symptom burden, and we can estimate a timeline from our symptoms. Misclassification can lead to wrong conclusions and suboptimal coping strategies such as taking medication that is either not helpful or harmful. Another example of misclassification would be failing to identify symptoms of a stroke, causing a delay in medical intervention with potentially fatal consequences.
The project is of theoretical relevance by targeting fundamental processes linking anxiety and interoception such as classification strategies and excessive intra-category generalisation. Identifying these links is relevant to understand misclassification of bodily sensations, for example in patients with medically unexplained symptoms, but also in patients misclassifying sensations that are the result of pathological processes.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

Individuals higher in intolerance of uncertainty, that is, individuals who tended to react with frustration and fear to uncertainty elicited by ambiguous information, tended to take a “better safe than sorry” strategy and were more likely to misclassify bodily sensations as belonging to a “high intensity” (versus “low intensity”) category. Furthermore, more anxious individuals and individuals scoring higher on intolerance of uncertainty expressed higher certainty about their classification decisions. Higher subjective certainty was related to lower accuracy in classification. Importantly, in longitudinal testing, repeating the same categorisation task twice with a week between sessions, we found that individuals who were more certain about their (often incorrect) classifications, did not improve in accuracy from one week to the next. Indeed, individuals who were highly certain that they “got it right” showed a tendency to perform less accurately in follow up tests. We found this effect for respiratory stimuli, for painful stimuli, as well as for visual stimuli showing angry facial expressions.
To summarise, our results suggest that anxiety is linked to interoception via processes of over-inclusive categories and liberal categorisation strategies. This process is mediated by intolerance of uncertainty, a trait that is positively related to anxiety and to fear of bodily sensations such as pain catastrophizing. We interpret findings of higher subjective certainty in individuals higher in anxiety and intolerance of certainty as a strategy to cope with the aversive feeling of uncertainty. Once a decision is made, uncertainty has been overcome. If this process, however, is rushed because processing of ambiguous information is perceived as too aversive, decisions may not be data-driven, but driven by overly general categorical information.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

An important clinical implication of our findings is that patients who admit to being unsure about the clinical relevance of their symptoms should not be discredited in the diagnostic process. Uncertainty may be an adequate reaction to symptoms that are often ambiguous in the early stages of a disease. Acknowledging uncertainty is the first step to more detailed sensory processing. Addressing intolerance of uncertainty in patients with medically unexplained symptoms may be beneficial in reducing fear of ambiguous bodily sensations as well as improving somatic decision strategies and classification.
This is one of the first projects to test Bayesian predictive coding theories in the field of interoception. State of the art research in interoception insists mostly on using external criteria such as an ECG in the heartbeat detection task (Domschke et al., 2010). Mapping perception with external measurements, however, means to ignore basic tenets of epistemology. Kant (1787/1998) complained that “it must still remain a scandal to philosophy and to the general human reason to be obliged to assume, as an article of mere belief, the existence of things external to ourselves (from which, yet, we derive the whole material of cognition for the internal sense), and not to be able to oppose a satisfactory proof to any one who may call it in question.” (p.29). He continues later on “For truth or illusory appearance does not reside in the object, in so far as it is intuited, but in the judgement upon the object, in so far as it is thought. It is, therefore, quite correct to say that the senses do not err, not because they always judge correctly, but because they do not judge at all.”(p.205). A model of the body and the body in its environment cannot be an “error”, it can only have a poor predictive value for future stimulation.
Heidegger (1927/1967) commented on Kant that “The 'scandal of philosophy' is not that this proof has yet to be given, but that such proofs are expected and attempted again and again.” (p. 249). We agree with von Helmholtz (1867/1961, p.85) that “Still to many physiologists and psychologists the connection between the sensation and the conception of the object usually appears to be so rigid and obligatory that they are not much disposed to admit that, to a considerable extent at least, it depends on acquired experience, that is, on psychic activity.”
With this project, we have provided further evidence that it is of paramount importance to educate patients, medical professionals, and psychologist that also in the perception of bodily sensations, there is no ‘scandal’ and there is no possible proof. Symptoms have to be accepted on faith because they present a model of the body developed by the brain based on prior experiences, not a measurement of the body by the brain. It is a scandal if patients have the feeling that they need to prove that they are suffering before they can receive help, while, in theory, psychology and philosophy agree that such a proof is impossible as well as irrelevant. This project goes beyond state of the art research and has wider societal implications by developing methods that allow testing perception of the body in a Bayesian framework, respecting the inherently relative nature of perception.

Illustration by Olivia Knapp