Tuesday, 11 May 2021

Social Approaches to Delusions (1): The Social Epistemological Conception of Delusion

Today's post is by Kengo Miyazono (Hokkaido University) and it is the first in the series “Social Approaches to Delusions”. Here Kengo talks about his new paper with Alessandro Salice (University College Cork) “Social Epistemological Conception of Delusion” (open access in Synthese).


Kengo Miyazono


The dominant conception of delusion in psychiatry (in textbooks, research papers, diagnostic manuals, etc.) is predominantly epistemic (Broome & Bortolotti 2009). Delusions are almost always characterized in terms of some epistemic notion, e.g., evidence, reasoning, judgment, etc. For instance, DSM-5 characterizes delusions as “fixed beliefs that are not amenable to change in light of conflicting evidence” (italics added: p. 87), and they are said to be “based on incorrect inference about external reality” and “firmly held despite what almost everyone else believes and despite what constitutes incontrovertible and obvious proof or evidence to the contrary” (italics added: p. 819).


There is, however, an individualistic bias in the epistemic conception of delusions in psychiatry; the epistemic conception tends to characterize delusion in terms of individualistic sources of evidence (e.g. perception, reasoning, memory, etc.) rather than social sources of evidence (e.g. testimony, peer disagreement, etc.). DSM-5, for examples, characterizes delusions in terms of a failure of inference, not in terms of a failure of testimony.

The same bias, i.e., the individualistic bias, had been pervasive in philosophical epistemology until recently; the bias consists in thinking of an epistemic agent as “a single individual who undertakes the task [of seeking truth] all by himself/herself, without consulting others” (Goldman and O’Connor 2019). Against this bias, social epistemologists propose an alternative conception of the epistemic agent as someone who “pursue[s] the truth […] with the help of, or in the face of, others” (Goldman and O’Connor 2019).


We endorse the social epistemological turn in philosophical epistemology and claim that a corresponding turn is needed in the study of delusions. It is a turn from the (purely) individualistic study of delusion in which only individualistic sources of evidence (e.g., perception, reasoning) are investigated to the (partially) social study of delusion in which social sources of evidence (e.g., testimony) are also investigated.

Alessandro Salice


My recent paper with Alessandro Salice is intended as an initial step toward such a social epistemological turn in the study of delusions. This paper presents a new model of the etiology of delusions (the “testimonial theory of delusions”) according to which delusions in schizophrenia are partially explained by testimonial abnormalities, including (1) the loss of testimonial interaction with others (“testimonial isolation”) and (2) the discounting of testimonial evidence (“testimonial discount”). Both testimonial isolation and testimonial discount are general tendencies in schizophrenia, caused by social abnormalities characterizing the disorder.

Our project is coherent with some recent papers, including “Bayesian Psychiatry and the Social Focus of Delusions” by Daniel Williams and Marcella Montagnese, “De-Rationalising Delusions” by Vaughan Bell, Nichola Raihani, and Sam Wilkinson, and “Expressivism about Delusion Attribution” by Sam Wilkinson. I share Williams and Montagnese’s skepticism about content-neutral, domain-general Bayesian account of delusion. Testimonial abnormalities might be domain specific and dissociable from general reasoning abnormalities.

I am also sympathetic to the claim by Bell, Raihani, and Wilkinson that alterations to coalitional cognition play important roles in delusion formation process. Testimonial abnormalities might be understood as one of the consequences of alterations to coalitional cognition. And Wilkinson’s expressivism about delusion attribution can fruitfully be combined with the testimonial theory of delusions. A person X’s expressive act of attributing delusions to another person Y can be understood as X’s reaction to (among others) testimonial abnormalities that are exhibited by Y.

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