In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 11.1 (2004) 65-70 [Access article in PDF] Top-Down and Bottom-Up in Delusion Formation Jakob Hohwy Keywords delusions, top-down, bottom-up, predictive coding Some delusions may arise as responses to unusual experiences (Davies et al. 2001; Maher 1974;). The implication is that delusion formation in some cases involves some kind of bottom-up mechanism—roughly, from perception to belief. Delusion formation may also involve some kind of top-down mechanism. (...) This could be in the shape of a patient's flawed background beliefs, or biases, which somehow modulate perception or ensure delusional interpretations of experience. There is little agreement about what kind of mechanism is primary in delusion formation, or, indeed, what the particular mechanisms and their neural substrates might be.In the evaluation of top-down and bottom-up mechanisms in delusion formation, a number of conceptual questions should be addressed (Davies and Coltheart 2000). For example, if there is an experiential component, why is a hypothesis with a delusional explanation of the unusual experience seen as relevant? Why do the subjects come to believe it tenaciously? How come some unusual experiences do not develop into delusions?A number of empirical findings also need to be taken into account: for example, the damage to the autonomic system in Capgras delusion (Ellis et al. 1997), the decreased ability for fast error correction in schizophrenia (Frith and Done 1989), modulation of activity in parietal cortex in delusions of alien control and other passivity experiences (Blakemore, Oakley, and Frith 2003), and also in schizophrenia, the increased sensitivity to self-produced stimuli, such as tickling oneself (Blakemore et al. 2000) and the sound of one's own voice (Ford et al. 2001).Theory choice can also be guided by philosophical doctrines about, for example, the nature of belief, the constitutive role of rationality, and intersubjectivity and the nature of judgements about the external world. It is natural, however, to let beliefs about philosophical doctrine be secondary to empirical findings and conceptual issues.The distinction between bottom-up and top-down mechanisms is particularly sharp in John Campbell's (2001) account of delusions and in Tim Bayne and Elisabeth Pacherie's (2004) discussion of Campbell. In this discussion, top-down approaches are associated with the general philosophical doctrine of rationalism, and bottom-up approaches with the philosophical doctrine of empiricism. Campbell's account is top-down because he posits delusional framework beliefs that arise directly as a result of brain damage or malfunction, and that work in some top-down fashion on the interpretation of experience. Bayne [End Page 65] and Pacherie convincingly defend empiricism against Campbell's rationalist account. Among their many other objections, they briefly puzzle about how a delusional framework belief (e.g., that one's spouse is an impostor) in a top-down fashion could cause the damage to the autonomic system seen in the Capgras and Cotard delusions (2004, 1). I think this is a very important objection because skin conductance data are part of the evidence for the bottom-up hypothesis concerning the Capgras delusion. We could add to this, for example, that it is mysterious how belief in a top-down fashion could cause people with schizophrenia to be worse at fast error correction than normal controls, to be better at tickling themselves than normal controls, and to have an increased response to the sound of their own voice.On the other hand, although the skin conductance response (SCR) evidence suggests a bottom-up approach to the Capgras delusion, it does not explain the character of the subjective experience that is hypothesized to give rise to the delusional belief: reduced SCR is not part of the experience itself (thanks to Ian Gold for discussion of this). Something more is required to give a full account of the type of experience that gives rise to the delusion. Further, as they stand, most bottom-up accounts are unable to account for why reality testing fails for beliefs based on these experiences.Neither rationalism nor empiricism on their own seem able to address the conceptual questions while paying... (shrink)

In lieu of an abstract, here is a brief excerpt of the content:Philosophy, Psychiatry, & Psychology 11.1 (2004) 65-70 [Access article in PDF] Top-Down and Bottom-Up in Delusion Formation Jakob Hohwy Keywords delusions, top-down, bottom-up, predictive coding Some delusions may arise as responses to unusual experiences (Davies et al. 2001; Maher 1974;). The implication is that delusion formation in some cases involves some kind of bottom-up mechanism—roughly, from perception to belief. Delusion formation may also involve some kind of top-down mechanism. (...) This could be in the shape of a patient's flawed background beliefs, or biases, which somehow modulate perception or ensure delusional interpretations of experience. There is little agreement about what kind of mechanism is primary in delusion formation, or, indeed, what the particular mechanisms and their neural substrates might be.In the evaluation of top-down and bottom-up mechanisms in delusion formation, a number of conceptual questions should be addressed (Davies and Coltheart 2000). For example, if there is an experiential component, why is a hypothesis with a delusional explanation of the unusual experience seen as relevant? Why do the subjects come to believe it tenaciously? How come some unusual experiences do not develop into delusions?A number of empirical findings also need to be taken into account: for example, the damage to the autonomic system in Capgras delusion (Ellis et al. 1997), the decreased ability for fast error correction in schizophrenia (Frith and Done 1989), modulation of activity in parietal cortex in delusions of alien control and other passivity experiences (Blakemore, Oakley, and Frith 2003), and also in schizophrenia, the increased sensitivity to self-produced stimuli, such as tickling oneself (Blakemore et al. 2000) and the sound of one's own voice (Ford et al. 2001).Theory choice can also be guided by philosophical doctrines about, for example, the nature of belief, the constitutive role of rationality, and intersubjectivity and the nature of judgements about the external world. It is natural, however, to let beliefs about philosophical doctrine be secondary to empirical findings and conceptual issues.The distinction between bottom-up and top-down mechanisms is particularly sharp in John Campbell's (2001) account of delusions and in Tim Bayne and Elisabeth Pacherie's (2004) discussion of Campbell. In this discussion, top-down approaches are associated with the general philosophical doctrine of rationalism, and bottom-up approaches with the philosophical doctrine of empiricism. Campbell's account is top-down because he posits delusional framework beliefs that arise directly as a result of brain damage or malfunction, and that work in some top-down fashion on the interpretation of experience. Bayne [End Page 65] and Pacherie convincingly defend empiricism against Campbell's rationalist account. Among their many other objections, they briefly puzzle about how a delusional framework belief (e.g., that one's spouse is an impostor) in a top-down fashion could cause the damage to the autonomic system seen in the Capgras and Cotard delusions (2004, 1). I think this is a very important objection because skin conductance data are part of the evidence for the bottom-up hypothesis concerning the Capgras delusion. We could add to this, for example, that it is mysterious how belief in a top-down fashion could cause people with schizophrenia to be worse at fast error correction than normal controls, to be better at tickling themselves than normal controls, and to have an increased response to the sound of their own voice.On the other hand, although the skin conductance response (SCR) evidence suggests a bottom-up approach to the Capgras delusion, it does not explain the character of the subjective experience that is hypothesized to give rise to the delusional belief: reduced SCR is not part of the experience itself (thanks to Ian Gold for discussion of this). Something more is required to give a full account of the type of experience that gives rise to the delusion. Further, as they stand, most bottom-up accounts are unable to account for why reality testing fails for beliefs based on these experiences.Neither rationalism nor empiricism on their own seem able to address the conceptual questions while paying... (shrink)

Some monothematic types of delusions may arise because subjects have unusual experiences. The role of this experiential component in the pathogenesis of delusion is still not understood. Focussing on delusions of alien control, we outline a model for reality testing competence on unusual experiences. We propose that nascent delusions arise when there are local failures of reality testing performance, and that monothematic delusions arise as normal responses to these. In the course of this we address questions concerning the tenacity with (...) which delusions are maintained, their often bizarre content, the patients' inability to dismiss them, and their often circumscribed character. (shrink)

Bortolotti’s Delusions and Other Irrational Beliefs defends the view that delusions are beliefs on a continuum with other beliefs. A different view is that delusions are more like illusions, that is, they arise from faulty perception. This view, which is not targeted by the book, makes it easier to explain why delusions are so alien and disabling but needs to appeal to forensic aspects of functioning.

Probabilistic models have much to offer to philosophy. We continually receive information from a variety of sources: from our senses, from witnesses, from scientific instruments. When considering whether we should believe this information, we assess whether the sources are independent, how reliable they are, and how plausible and coherent the information is. Bovens and Hartmann provide a systematic Bayesian account of these features of reasoning. Simple Bayesian Networks allow us to model alternative assumptions about the nature of the information sources. (...) Measurement of the coherence of information is a controversial matter: arguably, the more coherent a set of information is, the more confident we may be that its content is true, other things being equal. The authors offer a new treatment of coherence which respects this claim and shows its relevance to scientific theory choice. Bovens and Hartmann apply this methodology to a wide range of much discussed issues regarding evidence, testimony, scientific theories, and voting. Bayesian Epistemology is an essential tool for anyone working on probabilistic methods in philosophy, and has broad implications for many other disciplines. (shrink)

If one formulates Helmholtz's ideas about perception in terms of modern-day theories one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. Using constructs from statistical physics it can be shown that the problems of inferring what cause our sensory inputs and learning causal regularities in the sensorium can be resolved using exactly the same principles. Furthermore, inference and learning can proceed in a biologically plausible fashion. The ensuing scheme rests on (...) Empirical Bayes and hierarchical models of how sensory information is generated. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of the brain's organisation and responses. In this paper, we suggest that these perceptual processes are just one emergent property of systems that conform to a free-energy principle. The free-energy considered here represents a bound on the surprise inherent in any exchange with the environment, under expectations encoded by its state or configuration. A system can minimise free-energy by changing its configuration to change the way it samples the environment, or to change its expectations. These changes correspond to action and perception, respectively, and lead to an adaptive exchange with the environment that is characteristic of biological systems. This treatment implies that the system's state and structure encode an implicit and probabilistic model of the environment. We will look at models entailed by the brain and how minimisation of free-energy can explain its dynamics and structure. (shrink)

If one formulates Helmholtz’s ideas about perception in terms of modern-day theories one arrives at a model of perceptual inference and learning that can explain a remarkable range of neurobiological facts. Using constructs from statistical physics it can be shown that the problems of inferring what cause our sensory inputs and learning causal regularities in the sensorium can be resolved using exactly the same principles. Furthermore, inference and learning can proceed in a biologically plausible fashion. The ensuing scheme rests on (...) Empirical Bayes and hierarchical models of how sensory information is generated. The use of hierarchical models enables the brain to construct prior expectations in a dynamic and context-sensitive fashion. This scheme provides a principled way to understand many aspects of the brain’s organisation and responses. In this paper, we suggest that these perceptual processes are just one emergent property of systems that conform to a free-energy principle. The free-energy considered here represents a bound on the surprise inherent in any exchange with the environment, under expectations encoded by its state or configuration. A system can minimise free-energy by changing its configuration to change the way it samples the environment, or to change its expectations. These changes correspond to action and perception, respectively, and lead to an adaptive exchange with the environment that is characteristic of biological systems. This treatment implies that the system’s state and structure encode an implicit and probabilistic model of the environment. We will look at models entailed by the brain and how minimisation of free-energy can explain its dynamics and structure. (shrink)

Addresses ‘too-odd-not-to-be-true’ reasoning in the assessment of testimony. This is the curious phenomenon that an initially less plausible report from multiple independent witnesses may elicit more confidence than an initially more plausible report.

In rubber hand illusions and full body illusions, touch sensations are projected to non-body objects such as rubber hands, dolls or virtual bodies. The robustness, limits and further perceptual consequences of such illusions are not yet fully explored or understood. A number of experiments are reported that test the limits of a variant of the rubber hand illusion. Methodology/Principal Findings -/- A variant of the rubber hand illusion is explored, in which the real and foreign hands are aligned in personal (...) space. The presence of the illusion is ascertained with participants' scores and temperature changes of the real arm. This generates a basic illusion of touch projected to a foreign arm. Participants are presented with further, unusual visuotactile stimuli subsequent to onset of the basic illusion. Such further visuotactile stimulation is found to generate very unusual experiences of supernatural touch and touch on a non-hand object. The finding of touch on a non-hand object conflicts with prior findings, and to resolve this conflict a further hypothesis is successfully tested: that without prior onset of the basic illusion this unusual experience does not occur. Conclusions/Significance -/- A rubber hand illusion is found that can arise when the real and the foreign arm are aligned in personal space. This illusion persists through periods of no tactile stimulation and is strong enough to allow very unusual experiences of touch felt on a cardboard box and experiences of touch produced at a distance, as if by supernatural causation. These findings suggest that one's visual body image is explained away during experience of the illusion and they may be of further importance to understanding the role of experience in delusion formation. The findings of touch on non-hand objects may help reconcile conflicting results in this area of research. In addition, new evidence is provided that relates to the recently discovered psychologically induced temperature changes that occur during the illusion. (shrink)

In this book Daniel Wegner offers a novel understanding of the relation of consciousness, the will, and our intentional and voluntary actions. Wegner claims that our experience and common sense view according to which we can influence our behavior roughly the way we experience that we do it is an illusion.

Delusions play a fundamental role in the history of psychology, philosophy and culture, dividing not only the mad from the sane but reason from unreason. Yet the very nature and extent of delusions are poorly understood. What are delusions? How do they differ from everyday errors or mistaken beliefs? Are they scientific categories? In this superb, panoramic investigation of delusion Jennifer Radden explores these questions and more, unravelling a fascinating story that ranges from Descartes’s demon to famous first-hand accounts of (...) delusion, such as Daniel Schreber’s Memoirs of My Nervous Illness. Radden places delusion in both a clinical and cultural context and explores a fascinating range of themes: delusions as both individually and collectively held, including the phenomenon of folies á deux ; spiritual and religious delusions, in particular what distinguishes normal religious belief from delusions with religious themes; how we assess those suffering from delusion from a moral standpoint; and how we are to interpret violent actions when they are the result of delusional thinking. As well as more common delusions, such as those of grandeur, she also discusses some of the most interesting and perplexing forms of clinical delusion, such as Cotard and Capgras. (shrink)

Delusions are a common symptom of schizophrenia and dementia. Though most English dictionaries define a delusion as a false opinion or belief, there is currently a lively debate about whether delusions are really beliefs and indeed, whether they are even irrational. The book is an interdisciplinary exploration of the nature of delusions. It brings together the psychological literature on the aetiology and the behavioural manifestations of delusions, and the philosophical literature on belief ascription and rationality. The thesis of the book (...) is that delusions are continuous with ordinary beliefs, a thesis that could have important theoretical and practical implications for psychiatric classification and the clinical treatment of subjects with delusions. By bringing together recent work in philosophy of mind, cognitive psychology and psychiatry, the book offers a comprehensive review of the philosophical issues raised by the psychology of normal and abnormal cognition, defends the doxastic conception of delusions, and develops a theory about the role of judgements of rationality and of attributions of self-knowledge in belief ascription. Presenting a highly original analysis of the debate on the nature of delusions, this book will interest philosophers of mind, epistemologists, philosophers of science, cognitive scientists, psychiatrists, and mental health professionals. (shrink)

Genes adjacent to species-specific loci are 6.2% older than genes adjacent to other dynamic loci (P < 10−2 by randomization; gray bars in Fig. 3); thus, species-specific genes are not randomly distributed but are found preferentially in the older regions, indicating that the incipient Escherichia and Salmonella lineages continued to participate in recombination at loci unlinked to lineage-specific genes.

Does the formation of delusions involve abnormal reasoning? According to the prominent ‘two-factor’ theory of delusions (e.g. Coltheart, 2007), the answer is yes. The second factor in this theory is supposed to affect a deluded individual's ability to evaluate candidates for belief. However, most published accounts of the two-factor theory have not said much about the nature of this second factor. In an effort to remedy this shortcoming, Coltheart, Menzies and Sutton (2010) recently put forward a Bayesian account of inference (...) in delusions. I outline some criticisms of this important account, and sketch an alternative account of delusional inference that, I argue, avoids these criticisms. Specifically, I argue that the second factor in delusion formation involves a systematic deviation from Bayesian updating, a deviation that may be characterized as a bias towards ‘explanatory adequacy’. I present a numerical model of this idea and show that my alternative account is broadly consistent with prominent prediction error models of delusion formation (e.g. Corlett, Murray et al., 2007). (shrink)