Monothematic Delusions: Towards a Two-Factor Account

Abstract

We provide a battery of examples of delusions against which theoretical accounts can be tested. Then we identify neuropsychological anomalies that could produce the unusual experiences that may lead, in turn, to the delusions in our battery. However, we argue against Maher's view that delusions are false beliefs that arise as normal responses to anomalous experiences. We propose, instead, that a second factor is required to account for the transition from unusual experience to delusional belief. The second factor in the etiology of delusions can be described superficially as a loss of the ability to reject a candidate for belief on the grounds of its implausibility and its inconsistency with everything else that the patient knows, but we point out some problems that confront any attempt to say more about the nature of this second factor.

Failing to self-ascribe thought and motion: Towards a three-factor account of passivity symptoms in schizophrenia

“…As noted by Davies and Coltheart (2000) several delusions can be categorized as monothematic in that they focus on a central theme (Davies et al, 2001). Examples of monothematic delusions include Capgras Delusion (the belief that individuals close to the person have been replaced by imposters) reduplicative paramnesia (an arm [attached to me] is someone else's and that person has three arms), the Cotard Delusion (the belief that I am dead), thought insertion, and alien control.…”

I move, therefore I am: A new theoretical framework to investigate agency and ownership

“…Here, neuropsychological anomalies in perceptual or affective processing are insufficient to explain the intrinsic nature of delusions, namely the fact that (i) an alien experience is not accepted as a strange experience, that (ii) a delusional agency hypothesis about the perceived fact is formed and that (iii) this is maintained despite different stored encyclopedic knowledge about the own behavior and despite the testimony of others (cf. Davies, Coltheart, Langdon, & Breen, 2001). These features can only be explained by a misbalanced integration of different cognitive cues, in particular background beliefs, contextual cues and action intentions.…”

Phenomenology and delusions: Who put the ‘alien’ in alien control?

“…Perhaps, as Davies et al (2001) suggest, delusional individuals might have difficulties inhibiting the pre-potent doxastic response to their experiences. Seeing is certainly not believing, but the transition from perceiving 'that P' to believing 'that P' is a familiar and attractive one.…”

“…Two-deficit accounts, by contrast, hold that delusional patients have belief-fixation processes that are outside the normal range. The distinction between one and two-deficit accounts is orthogonal to the distinction between explanationist and endorsement accounts (Davies et al 2001). Both endorsement and explanationist models can be developed in either onedeficit or two-deficit terms.…”

“…Similarly, the Cotard delusion (which involves the belief that one is dead or unreal in some way) may stem from a general flattening of affective responses to external stimuli (Ellis & Young, 1990), while the seed of the Frégoli delusion (the belief that one is being followed by known people who are in disguise) may lie in heightened affective responses to unfamiliar faces (Davies et al, 2001). Experience-based proposals have been provided for a number of other delusions (Breen et al, 2000;Breen et al 2001;Stone & Young, 1997;Maher, 1988;Davies, 2001;Davies et al, 2005;Langdon & Coltheart, 2000).…”