Periodic Reporting for period 1 - CIP (Categorical Interoception Project: How generalization and classification strategies link anxiety and interoception)
Période du rapport: 2016-04-01 au 2018-03-31
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.
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.
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.