هذیان کپگراس: مدل تعامل گرایی

In this paper I discuss the role played by disturbed phenomenology in accounting for the formation and maintenance of the Capgras delusion. Whilst endorsing a two-stage model to explain the condition, I nevertheless argue that traditional accounts prioritise the role played by some form of second-stage cognitive disruption at the expense of the significant contribution made by the patient’s disturbed phenomenology, which is often reduced to such uninformative descriptions as “anomalous” or “strange”. By advocating an interactionist model, I argue that the delusional belief constitutes an attempt on the part of the patient to explain his/her initially odd and somewhat disturbed phenomenal content (which I refer to as a sense of estrangement) and, moreover, that the delusion then structures the patient’s experience such that what he/she perceives is an impostor. This fact is used to explain the delusional belief’s maintenance and resistance to revision. Thus, whilst accepting that second-stage cognitive disruption has a part to play in explaining the Capgras delusion, the emphasis here is placed on the role played by the patient’s changing phenomenal content and its congruence with the delusional belief. Unlike traditional two-stage models, which posit a unidirectional progression from experience to belief, the interactionist model advocates a two-way interaction between bottom-up and top-down processes. The application of this model to other delusional beliefs is also considered.

Over the past decade or so, much discussion on the Capgras delusion—the belief that relatives and/or significant others have been replaced by an impostor (Capgras & Reboul-Lachaux, 1923)—has focused on the extent to which abnormal phenomenology can account for the formation of delusional belief (Bayne & Pacherie, 2004b). In line with this debate, I will argue that approaches which take into account the patient’s disturbed phenomenology either (i) overemphasise the extent to which the anomalous nature of the experiential content can cause directly the delusional belief (indicative of a one-stage account), or (ii) assign such content a peripheral role in favour of some form of cognitive disruption. The marginalisation of disturbed phenomenology (as noted by ii) is particularly pronounced in two-stage models in which experiential content receives fairly cursory treatment and is described simply as “anomalous” or “bizarre”, or as a “strange feeling” that alludes to something being “not quite right”. In addition, and of equal importance to this paper, is the fact that each of these general approaches posits a causal explanation that is unidirectional in so far as it maps the causal progression exclusively from anomalous experience to delusional belief.1 It is my contention that the phenomenology of the Capgras patient has a much greater role to play in explaining the condition than two-stage models thus far allow. Having said that, it is not my intention to overburden the patient’s disturbed phenomenology with an explanatory role it cannot accommodate. What I propose is a two-stage model that features a two-way interaction between bottom-up and top-down processing rather than the more typical unidirectional aetiology found in other approaches. The significance of this interactionist model is that it transforms the nature of the patient’s experiential content from something “anomalous” (what, in Section 5, I refer to as ‘estrangement’) into a full-blown ‘impostor’ experience. In other words, the interactionist model, much like the more traditional two-stage model, posits that the Capgras patient forms the delusional belief that the woman in front of him (his wife) is an impostor through a combination of disturbed phenomenology and cognitive deficit but, in addition, makes the bolder claim that the belief is maintained because the patient, upon forming the delusional belief, experiences his wife as an impostor. 2 To help present the case for the interactionist model, it is necessary to provide some detail (however brief) on current thinking about the Capgras delusion. In Sections 2, 3 and 4, I will outline issues relating to one- and two-stage models, neurological dysfunction in the Capgras patient that is said to ‘mirror’ prosopagnosia, evidence for reduced autonomic arousal and the implications this has for the patient’s underlying phenomenology. A more detailed analysis of the patient’s experiential content—beyond merely “anomalous”—will also be undertaken (see Sections 5, 6, 7 and 8) lending support for the two-way causal interaction proposed above. Finally, in Section 9, the model’s application to other cases of delusional misidentification will be discussed.

In conclusion, the interactionist model advocates a more prominent role for patient phenomenology in accounting for the formation and maintenance of delusional beliefs than previous two-stage models have allowed. This, however, is not at the expense of overburdening the patient’s disturbed phenomenology with an explanatory role it cannot satisfy—a criticism of the one-stage model. In relation to the Capgras delusion, which has been the main feature of this paper, by highlighting differences in the salience of Capgras and prosopagnosic patient experience, I hope to have progressed our understanding of the underlying phenomenology of the condition beyond a mere anomalous experience to something more causally potent and explanatorily significant. In particular, my distinction between a lack and loss of affect, how this stems from reduced SCR, and how it pervades consciousness in the form of a sense of estrangement, contribute to a more detailed understanding of why the delusional belief is formed. In addition, despite my insistence that the focus of this paper should be on the role played by the patient’s phenomenal experience in accounting for the Capgras delusion, I have not wavered in my support for some form of second-stage cognitive disruption. I have even introduced another form of cognitive bias to help explain the maintenance of the delusional belief. It is worth noting, however, that confirmatory bias is considered a normal part of one’s cognitive function, even if problems arise from time to time because of it. I see no reason to argue against its normal use in the Capgras patient, even if the cognitive process that contributed to the formation of the delusional belief (that the normal process of confirmatory bias is seeking to confirm) is itself dysfunctional. Likewise, the patient’s predilection towards observational data need not be pathological, and need not be the result of failure to inhibit the pre-potent doxastic response. A tendency to favour observational data typically serves us well, and is questioned only (or for the most part) when it contradicts our beliefs. What I have argued throughout is that the impostor belief, although formed as a result of some form of cognitive disruption, actually (re)structures the experience, making belief and experience congruent. The experience validates the belief, and the experience is believed to be authentic, a process that I have applied to account for other monothematic delusions.