After reviewing factors implicated in the generation of delusional beliefs, we conclude that whilst a perceptual aberration coupled with a particular type of attri‐butional bias may be necessary to explain the specific thematic content of a bizarre delusion, neither of these factors, whether in isolation or in combination, is sufficient to explain the presence of delusional beliefs. In contrast to bias models (theories which explain delusion formation in terms of extremes of normal reasoning biases), we advocate a deficit model of (...) delusion formation–that is, delusions arise when the normal cognitive system which people use to generate, evaluate, and then adopt beliefs is damaged. Mere bias we think inadequate to explain bizarre delusions which defy commonsense and persist despite overwhelming rational counter‐argument. In particular, we propose that two deficits must be present in the normal cognitive system to explain bizarre delusions: (1) there must be some damage to sensory and/or attentional‐orient‐ing mechanisms which causes an aberrant perception–this explains the bizarre content of the causal hypothesis generated to explain what is happening; and (2) there must also be a failure of normal belief evaluation–this explains why a hypothesis, implausible in the light of general commonsense, is adopted as belief. This latter deficit occurs, we suggest, when an individual is incapable of suspending the natural favoured status of direct first‐person evidence in order to critically evaluate hypotheses, given equal pri‐ority whether based on direct or indirect sources of information. In contrast, delusions with ‘ordinary’ content may arise when a single deficit of normal belief evaluation occurs in the context of an extreme (but normal) attentional bias, thus causing failure to critically evaluate hypotheses based on misperceptions and misintrepretations of ambiguous (but ordinary) first‐person experience. (shrink)

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 (...) aetiology 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. (shrink)

Delusional beliefs have sometimes been considered as rational inferences from abnormal experiences. We explore this idea in more detail, making the following points. Firstly, the abnormalities of cognition which initially prompt the entertaining of a delusional belief are not always conscious and since we prefer to restrict the term “experience” to consciousness we refer to “abnormal data” rather than “abnormal experience”. Secondly, we argue that in relation to many delusions (we consider eight) one can clearly identify what the abnormal cognitive (...) data are which prompted the delusion and what the neuropsychological impairment is which is responsible for the occurrence of these data; but one can equally clearly point to cases where this impairments is present but delusion is not. So the impairment is not sufficient for delusion to occur. A second cognitive impairment, one which impairs the ability to evaluate beliefs, must also be present. Thirdly (and this is the main thrust of our chapter) we consider in detail what the nature of the inference is that leads from the abnormal data to the belief. This is not deductive inference and it is not inference by enumerative induction; it is abductive inference. We offer a Bayesian account of abductive inference and apply it to the explanation of delusional belief. (shrink)

In this book, psychologists and philosophers describe and discuss a range of case studies of delusional beliefs, drawing out general lessons both for the cognitive architecture of the mind and for the notion of rationality, and exploring connections between the delusional beliefs that occur in schizophrenia and the flawed understanding of beliefs that is characteristic of autism.

INTRODUCTION: In accounts of the two-factor theory of delusional belief, the second factor in this theory has been referred to only in the most general terms, as a failure in the processes of hypothesis evaluation, with no attempt to characterise those processes in any detail. Coltheart and Davies attempted such a characterisation, proposing a detailed eight-step model of how unexpected observations lead to new beliefs based on the concept of abductive inference as introduced by Charles Sanders Peirce. METHODS: In (...) this paper, we apply that model to the explanation of various forms of delusional belief. RESULTS: We provide evidence that in cases of delusion there is a specific failure of the seventh step in our model: the step at which predictions from hypotheses are considered in the light of relevant evidence. CONCLUSIONS: In the two-factor theory of delusional belief, the second factor consists of a failure to reject hypotheses in the face of disconfirmatory evidence. (shrink)

Some delusional patients exhibit only a single delusional belief (or several delusional beliefs concerning a single theme): this is monothematic delusion. It contrasts with polythematic delusion, where the patient exhibits a variety of delusions concerning a variety of different themes. The neuropsychological bases of various monothematic delusions are rather well understood, and there is a well-worked-out general neuropsychological theory of monothematic delusion, the two-factor theory. Whether polythematic delusion might be explained in a similar way is an open question: I sketch (...) some possible ways in which a comparable two-factor account might be developed for polythematic (‘psychiatric’) delusional conditions such as delusions of reference. (shrink)

In this article, we propose a pluralistic approach to the explanation of social understanding that integrates literature from social psychology with the theory of mind debate. Social understanding in everyday life is achieved in various ways. As a rule of thumb we propose that individuals make use of whatever procedure is cognitively least demanding to them in a given context. Aside from theory and simulation, associations of behaviors with familiar agents play a crucial role in social understanding. This role has (...) been neglected so far. We illustrate the roles of fluency and associations in social understanding in false belief tasks. (shrink)

The impact of our desires and preferences upon our ordinary, everyday beliefs is well-documented [Gilovich, T. . How we know what isn’t so: The fallibility of human reason in everyday life. New York: The Free Press.]. The influence of such motivational factors on delusions, which are instances of pathological misbelief, has tended however to be neglected by certain prevailing models of delusion formation and maintenance. This paper explores a distinction between two general classes of theoretical explanation for delusions; the motivational (...) and the deficit. Motivational approaches view delusions as extreme instances of self-deception; as defensive attempts to relieve pain and distress. Deficit approaches, in contrast, view delusions as the consequence of defects in the normal functioning of belief mechanisms, underpinned by neuroanatomical or neurophysiological abnormalities. It is argued that although there are good reasons to be sceptical of motivational theories , recent experiments confirm that motives are important causal forces where delusions are concerned. It is therefore concluded that the most comprehensive account of delusions will involve a theoretical unification of both motivational and deficit approaches. (shrink)

Are there universals of reading? There are three ways of construing this question. Is the region of the brain where reading is implemented identical regardless of what writing system the reader uses? Is the mental information-processing system used for reading the same regardless of what writing system the reader uses. Do the word's writing systems share certain universal features? Dehaene offers affirmative answers to all three questions in his book. Here I suggest instead that the answers should be negative. And (...) I ask: if reading is not universal in any sense, what does this imply about Dehaene's Neuronal Recycling hypothesis for reading? (shrink)

Over the past century or more, cognitive neuropsychologists have discussed many of the issues raised in this volume. On the basis of this literature, we argue that autism is not a single homogeneous condition, and so can have no single cause. Instead, each of its symptoms has a cause, and the proper study of autism is the separate study of each of these symptoms and its cause. We also offer evidence to support the radical view advanced by Stoljar and Gold (...) in this volume, namely, that in explaining such syndromes the cognitive level of explanation has priority over the neuroscientific. (shrink)

People acquire new beliefs in various ways. One of the most important of these is that new beliefs are acquired as a response to experiencing events that one did not expect. This involves a form of inference distinct from both deductive and inductive inference: abductive inference. The concept of abduction is due to the American pragmatist philosopher C. S. Peirce. Davies and Coltheart elucidated what Peirce meant by abduction, and identified two problems in his otherwise promising account requiring solution (...) if that account were to become fully workable. Here we propose solutions to these problems and offer an explicit cognitive model of how people derive new beliefs from observations of unexpected events, based on Peirce's work and Sokolov's ideas about prediction error triggering new beliefs. We consider that this model casts light not only upon normal processes of belief formation but also upon the formation of delusional beliefs. (shrink)

Article copyright 2002. 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. (shrink)

A recent article in this journal (Patterson & Plaut, 2009) argued that cognitive neuropsychology has told us very little over the past 30 or 40 years about “how the brain accomplishes its cognitive business.” This may well be true, but it is not important, because the principal aim of cognitive neuropsychology is not to learn about the brain. Its principal aim is instead to learn about the mind, that is, to elucidate the functional architecture of cognition. I show that this (...) is so (a) via extensive quotations from leading figures in this field and (b) by analysis of the subject matter of articles in the leading journal in the field, Cognitive Neuropsychology. Recent reviews of the past 25 years of work in this field (Coltheart & Caramazza, 2006) have concluded that cognitive neuropsychology has told us much about the functional architecture of cognition in a variety of cognitive domains. Patterson and Plaut (2009) did not consider this aim of cognitive neuropsychology. Therefore, their conclusions that cognitive neuropsychology has not been successful, and that this is because the particular methods it uses are flawed, are not justified. (shrink)

After reviewing factors implicated in the generation of delusional beliefs, we conclude that whilst a perceptual aberration coupled with a particular type of attri‐butional bias may be necessary to explain the specific thematic content of a bizarre delusion, neither of these factors, whether in isolation or in combination, is sufficient to explain the presence of delusional beliefs. In contrast to bias models (theories which explain delusion formation in terms of extremes of normal reasoning biases), we advocate a deficit model of (...) delusion formation–that is, delusions arise when the normal cognitive system which people use to generate, evaluate, and then adopt beliefs is damaged. Mere bias we think inadequate to explain bizarre delusions which defy commonsense and persist despite overwhelming rational counter‐argument. In particular, we propose that two deficits must be present in the normal cognitive system to explain bizarre delusions: (1) there must be some damage to sensory and/or attentional‐orient‐ing mechanisms which causes an aberrant perception–this explains the bizarre content of the causal hypothesis generated to explain what is happening; and (2) there must also be a failure of normal belief evaluation–this explains why a hypothesis, implausible in the light of general commonsense, is adopted as belief. This latter deficit occurs, we suggest, when an individual is incapable of suspending the natural favoured status of direct first‐person evidence in order to critically evaluate hypotheses, given equal pri‐ority whether based on direct or indirect sources of information. In contrast, delusions with ‘ordinary’ content may arise when a single deficit of normal belief evaluation occurs in the context of an extreme (but normal) attentional bias, thus causing failure to critically evaluate hypotheses based on misperceptions and misintrepretations of ambiguous (but ordinary) first‐person experience. (shrink)

There are universals of language; but is it also true, as the target article claims, that there are universals of reading? We believe there are no such universals, and invite others to refute our claim by providing a list of some universals of reading. If there are no universals of reading, there cannot be a universal model of reading.

Four detailed cases of delusions of misidentification (DM) are presented: two cases of misidentification of the reflected self, one of reverse intermetamorphosis, and one of reduplicative paramnesia. The cases are discussed in the context of three levels of interpretation: neurological, cognitive and phenomenological. The findings are compared to previous work with DM patients, particularly the work of Ellis and Young (1990; Young, 1998) who found that loss of the normal affective response to familiar faces was a contributing factor in the (...) Capgras delusion. The four cases presented suggest that this particular deficit is not a critical factor in the development of other forms of DM. (shrink)

The question posed by Dunn and Kirsner (D&K) is an instance of a more general one: What can we infer from data? One answer, if we are talking about logically valid deductive inference, is that we cannot infer theories from data. A theory is supposed to explain the data and so cannot be a mere summary of the data to be explained. The truth of an explanatory theory goes beyond the data and so is never logically guaranteed by the data. (...) This is not just a point about cognitive neuropsychology, or even about psychology in general. It is a familiar point about all science. (shrink)

In this book, psychologists and philosophers describe and discuss a range of case studies of delusional beliefs, drawing out general lessons both for the cognitive architecture of the mind and for the notion of rationality, and exploring connections between the delusional beliefs that occur in schizophrenia and the flawed understanding of beliefs that is characteristic of autism.

_Abstract_: Cognitive science is typically defined as the multidisciplinary study of mind, with the disciplines involved usually listed as philosophy, psychology, artificial intelligence, neuroscience, linguistics, and anthropology. Furthermore, these six “core disciplines” are generally regarded as having equal status vis-à-vis cognitive science. In contrast to the latter position, I argue that psychology has a special status here: it is central to cognitive science in a way that none of the other five disciplines is. I support this argument via both theoretical (...) and empirical considerations. _Keywords_: Psychology; Cognitive Science; Interdisciplinarity/Multidisciplinarity _La psicologia è – e dovrebbe essere – al centro della scienza cognitiva_ _Riassunto_: La scienza cognitiva viene definita comunemente come indagine multidisciplinare sulla mente e tra le discipline che vi sono coinvolte vengono solitamente indicate la filosofia, la psicologia, l’intelligenza artificiale, la neuroscienza, la linguistica e l’antropologia. Queste sei “discipline fondamentali” sono generalmente considerate come aventi pari dignità nell’ambito della scienza cognitiva. A dispetto di quest’ultima posizione sosterrò, invece, che alla psicologia vada riconosciuto uno status speciale: la sua importanza per la scienza cognitiva è tale da non poter essere eguagliata da nessuna delle altre cinque discipline. A supporto di questa posizione porterò alcune riflessioni di natura teoretica ed empirica. _Parole chiave_: Psicologia; Scienza cognitiva; Interdisciplinarità/Multidisciplinarità. (shrink)

The work reported in this paper investigated the putative functional dependence of pragmatic language skills on general mind‐reading capacity by testing theory‐of‐mind abilities and understanding of non‐literal speech in patients with schizophrenia and in healthy controls. Patients showed difficulties with inferring mental states on a false‐belief picture‐sequencing task and with understanding metaphors and irony on a story‐comprehension task. These difficulties were independent of low verbal IQ and a more generalised problem inhibiting prepotent information. Understanding of metaphors and understanding of irony (...) made significant and independent contributions to discriminating patients from controls, suggesting that metaphor and irony make distinct pragmatic demands. (shrink)

Beliefs may be true or false, and grounded or ungrounded. McKay & Dennett (M&D) treat these properties of belief as independent. What, then, do they mean by misbelief? They state that misbeliefs are So would they consider a very well-grounded belief that is false a misbelief? And why can't beliefs that are very poorly grounded be considered delusions, even when they are true?