In general, there appears to be considerable support (albeit disputed evidence) for the assumption that delusions are best understood as the result o f abnormal belief processes (e.g., Bentall et al., 2001; Freeman et al., 2001; Oltmanns & Maher, 1988).
Indeed, this assumption is frequently made without question or evidence (and as such could be considered a belief), by following the formal DSM-IV criteria. As Chapter 2 will demonstrate, these attempts to explain delusions typically use the construct of belief explicitly, and the growing continuum approach for psychotic symptoms (see section 1.6) within psychiatry implicitly assumes normal equivalents of delusions in the non-clinical population (Bentall, 2003).
However, several authors have questioned the definition of delusion in terms o f a deviant form o f belief. Spitzer (1990) comments that patients tend to state that they ‘know’ their delusions rather than ‘believe’ in them and suggests that to consider delusions as a subset or type of belief may therefore be unhelpful. However, this does not in itself suggest the lack of a belief (one might choose to use alternative vocabulary if asked to describe one’s beliefs, but that is not to say that one does not hold this as a belief). As discussed earlier with regard to the distinction between belief and knowledge, to ‘know’ something suggests objective and subjective evidence,
whereas to ‘believe’ implies only subjective, thus suggesting that (while choosing a stronger term than may be appropriate) these statements would still fulfil the proposed criteria for belief. Indeed, a statement that, e.g., ‘My wife has been replaced by an impostor’ would seem strong evidence for attributing a belief with this content to the individual concerned. Moreover, recent studies have found that the level of conviction with which delusions are held can fluctuate under questioning (Myin-Germeys et al., 2001), unlike those that might be expected for ‘knowledge’ (implying a more consistent level o f confidence). Instead it seems plausible that the conviction of a delusion may be similar to that o f other strongly held non-clinical beliefs.
Others have suggested delusions do not have sufficient conviction to qualify as a belief (e.g., Sass, 1994). They note that patients often maintain a detachment from their delusions, seeming to express these ideas ‘as i f they were true (Young, 1999).
However, these concerns presuppose that all beliefs must reach a prescribed level of conviction, which may not be appropriate. Investigations of the conviction with which a range of non-clinical beliefs are held would be useful to clarify this point.
Berrios (1991, p. 12) takes an even stronger position by claiming that clinical delusions are not beliefs but rather ‘empty speech acts ’, given that patients are often unable coherently to discuss the implications o f their delusions. In addition, patients do not always show appropriate emotional responses for their delusions (Sass, 1994).
For example, instead o f being distraught about his wife having been replaced, a patient with Capgras syndrome ‘specifically expressed thankfulness that she had located a substitute’ (Alexander et al., 1979, p.335). However, Stone and Young (1997) argue that even patients like that reported by Alexander and colleagues often retain some understanding o f the bizarreness o f the belief. Thus this is not an ‘empty
speech act’ in that patients recognise some of the impact of their delusion and the likely reactions it will evoke.
Nevertheless, Currie (2000) notes that delusions often ‘fa il to engage behaviour’ (p. 174), and suggests these are more akin to ‘imaginings’ that patients mistake for beliefs (although, again this could be true of non-clinical beliefs). Indeed, other authors have also argued that action resulting from delusional beliefs is rare (Anderson & Trethowan, 1973; Merskey, 1980; Slater & Roth, 1969). However, this is not true for all cases. Taylor (1985) found associations between delusions and violent offending, and one review reported this in 18% of cases of delusional misidentification (Forstl et al., 1991). Moreover, Buchanan and Wessely (2004) found that half o f their sample of patients with delusions reported having acted on these beliefs at least once. Furthermore, other subtler safety behaviours may be performed, to prevent the need for more overt actions in response to the delusional belief (Freeman, Garety et al., 2001). Indeed, (as discussed above when describing methodologies suitable for investigating beliefs) establishing a one-to-one correspondence between a belief and its consequential action is fraught with difficulties even in non-clinical cases. As such, whilst some patients with delusions are clearly not just voicing an ‘empty speech act’ and appear to have considerable insight, in others it is harder to determine the degree to which their delusion impacts onto their actions or emotions.
Indeed, several critics o f the claim that delusions constitute a form of belief acknowledge that some delusions seem best described as the result of dysfunctional belief processes (Currie, 2000; Sass, 1994; Young, 1999). Even Jaspers (1963), who described ‘delusion proper’ to be so distinct from ordinary phenomena as to be
‘psychologically irreducible ’ (1963, p. 96), acknowledged another set of beliefs,
delusion-like ideas, which he regarded as emerging ‘understandably from preceding affects’ (p. 96). Indeed, it is easier to see that delusions that seem to be extremes of normal cognitions (e.g., pathological jealousy) can be described as beliefs than those delusions that have bizarre content. These differences have led some authors (e.g., Mullen, 2003) to advocate more than one kind of delusion. Mullen suggests some delusions may be best regarded as distinct from normal belief, whereas others would be better viewed as comprising part of a continuum with normal beliefs.
This distinction has also been highlighted with regard to the delusion’s compatibility with the prior or co-existing beliefs held by the individual, tying in with the philosophical debate regarding atomism versus holism discussed earlier. Quine and Ullian (1970) proposed that all beliefs cohere to form a ‘web o f beliefs’. This implies that individuals should not be able to consciously hold (i.e., be aware of) contradictory beliefs. However, Stone and Young (1997) point out that some patients have fairly circumscribed delusions, particularly those with bizarre beliefs such as Cotard or Capgras (where the very bizarreness of the belief suggests contradictory beliefs may be held). Indeed, Bisiach (1988) describes a case where a patient with unilateral neglect insisted that his left arm was the examiner’s, even though this led him to the conclusion that the examiner must have three arms. Whilst some of these patients do form further delusions (e.g., one patient with Cotard delusion [‘I am dead’] developed the belief that he was in hell as a result o f the heat during a visit to South Africa: Young et al., 1992), for others their delusion seems relatively encapsulated.
These perspectives on the nature of delusion also have an impact on cognitive views o f modularity. Fodor (1983) suggested that belief formation was not a modular process, similar to other cognitive processes. He considered that beliefs need access to
all information to be reliable, meaning that informational encapsulation was not an option. Thus, taking a holist’s perspective, one might predict that holding a bizarre belief (e.g., Cotard) should impact onto the other beliefs held by an individual.
However, some monothematic delusions are reported as highly circumscribed or encapsulated and some others seemingly ‘coexist with beliefs they contradict' (Currie
& Jureidini, 2001, p. 160). Indeed, Jones (2003) argues that delusion formation does therefore show some o f the properties of a modular system, suggesting this is fast and informationally encapsulated.
However, others have suggested that monothematic delusions largely arise from anomalous perceptual experiences (e.g., Stone & Young, 1997). This is not a new idea - Kraepelin suggested this almost a century ago - but this hypothesis was recently developed further and brought to prominence by Maher (1988). Maher proposed that delusions arose as a result of attempting to account for anomalous experiences (AE). For example, in the case o f Capgras (the belief that someone, usually a close friend or relative, has been replaced by an impostor), the delusion is thought to result from a loss of the expected feeling of familiarity when perceiving a known face (Ellis & Young, 1990). If an individual was receiving frequent perceptual information that was consistent with this hypothesis, then this perceptual input may override the bias associated with coherence from other beliefs.
Indeed, Stone and Young (1997) note that belief formation is already subject to certain biases, so this is not a perfect system even in healthy individuals. Thus, given we are already aware o f the fallibility o f the system, the focus should be on whether biases are the same for patients with delusions as for healthy individuals.
Indeed, whilst inherently plausible, the extent to which belief coherence takes place in
healthy individuals is not known, and as such it is premature to claim any difference in the beliefs o f patients with delusions from normal belief processes.
Given that both beliefs and delusions can be defined in a multitude of ways, it is not surprising that comparisons between these two concepts are problematic. This is exacerbated by applying a strict definition of belief to a range of reported delusions, without any consideration that belief, as used by most individuals, can cover a spectrum o f conviction, stability and influence. Indeed, to examine the manner in which individuals report delusions and determine whether or not these are beliefs seems to necessitate investigating how people describe their beliefs. This issue will be considered further in Chapter 3.
Although there are outstanding questions regarding the similarity of formation processes for ‘normal’ beliefs and a minority of delusions (those that appear to be relatively circumscribed), the evidence seems on balance to suggest it is appropriate to view delusions as a form o f belief. Therefore throughout this thesis and following most authors (Davies et al., 2001; Langdon & Coltheart, 2000; van Os, 2003) and the official DSM definition (APA, 2000), delusions will be considered as one form of anomalous beliefs.
Consequently, the main research agenda remains to determine and/or elaborate the various factors that may cause a belief to be considered delusional. One approach that can be used to help determine the distinctions between delusions and other beliefs is by looking at psychiatric symptoms and/or syndromes as extremes on a continuum rather than categorically different from ‘normal’ beliefs and experiences. This continuum approach is discussed below.