Jakob Hohwy

Is it rational to believe that the mind is identical to the brain? Identity theorists say it is (or looks like it will be, once all the neuroscientific evidence is in), and they base this claim on a general epistemic route to belief in identity. I re-develop this general route and defend it against some objections. Then I discuss how rational belief in mind–brain identity, obtained via this route, can be threatened by an appropriately adjusted version of the anti-physicalist knowledge argument. Responses to this threat usually appeal either to different modes of presentation or to phenomenal concepts. But neither type of response is satisfactory. I provide a novel response, which appeals to an innocuous epistemic peculiarity of phenomenal states, namely their, as I shall call it, evidential insulation.

The notion that the brain is a prediction error minimizer entails, via the notion of Markov blankets and self-evidencing, a form of global scepticism — an inability to rule out evil demon scenarios. This type of scepticism is viewed by some as a sign of a fatally flawed conception of mind and cognition. Here I discuss whether this scepticism is ameliorated by acknowledging the role of action in the most ambitious approach to prediction error minimization, namely under the free energy principle. I argue that the scepticism remains but that the role of action in the free energy principle constrains the demon’s work. This yields new insights about the free energy principle, epistemology, and the place of mind in nature.

In this paper, we consider how certain longstanding philosophical questions about mental representation may be answered on the assumption that cognitive and perceptual systems implement hierarchical generative models, such as those discussed within the prediction error minimization framework. We build on existing treatments of representation via structural resemblance, such as those in Gładziejewski :559–582, 2016) and Gładziejewski and Miłkowski, to argue for a representationalist interpretation of the PEM framework. We further motivate the proposed approach to content by arguing that it is consistent with approaches implicit in theories of unsupervised learning in neural networks. In the course of this discussion, we argue that the structural representation proposal, properly understood, has more in common with functional-role than with causal/informational or teleosemantic theories. In the remainder of the paper, we describe the PEM framework for approximate Bayesian inference in some detail, and discuss how structural representations might arise within the proposed Bayesian hierarchies. After explicating the notion of variational inference, we define a subjectively accessible measure of misrepresentation for hierarchical Bayesian networks by appeal to the Kullbach–Leibler divergence between posterior generative and approximate recognition densities, and discuss a related measure of objective misrepresentation in terms of correspondence with the facts.

After being sorely neglected for some time, consciousness is well and truly back on the philosophical and scientific agenda. This entry provides a whistle-stop tour of some recent debates surrounding consciousness, with a particular focus on issues relevant to the scientific study of consciousness. The first half of this entry (the first to fourth sections) focuses on clarifying the explanandum of a science of consciousness and identifying constraints on an adequate account of consciousness; the second half of this entry (the fifth to seventh sections) examines a number of the methodological challenges facing the science of consciousness.

There is surprising evidence that introspection of our phenomenal states varies greatly between individuals and within the same individual over time. This puts pressure on the notion that introspection gives reliable access to our own phenomenology: introspective unreliability would explain the variability, while assuming that the underlying phenomenology is stable. I appeal to a body of neurocomputational, Bayesian theory and neuroimaging findings to provide an alternative explanation of the evidence: though some limited testing conditions can cause introspection to be unreliable, mostly it is our phenomenology itself that is variable. With this account of phenomenal variability, the occurrence of the surprising evidence can be explained while generally retaining introspective reliability

A new theory is taking hold in neuroscience. It is the theory that the brain is essentially a hypothesis-testing mechanism, one that attempts to minimise the error of its predictions about the sensory input it receives from the world. It is an attractive theory because powerful theoretical arguments support it, and yet it is at heart stunningly simple. Jakob Hohwy explains and explores this theory from the perspective of cognitive science and philosophy. The key argument throughout The Predictive Mind is that the mechanism explains the rich, deep, and multifaceted character of our conscious perception. It also gives a unified account of how perception is sculpted by attention, and how it depends on action. The mind is revealed as having a fragile and indirect relation to the world. Though we are deeply in tune with the world we are also strangely distanced from it.

Recent research has begun to investigate sensory processing in relation to nonclinical variation in traits associated with the autism spectrum disorders (ASD). We propose that existing accounts of autistic perception can be augmented by considering a role for individual differences in top-down expectations for the precision of sensory input, related to the processing of state-dependent levels of uncertainty. We therefore examined ASD-like traits in relation to the rubber-hand illusion: an experimental paradigm that typically elicits crossmodal integration of visual, tactile, and proprioceptive information in an unusual illusory context. Individuals with higher ASD-like traits showed reduced effects of the rubber-hand illusion on perceived arm position and reach-to-grasp movements, compared to individuals with lower ASD-like traits. These differences occurred despite both groups reporting the typical subjective experience of the illusion concerning visuotactile integration and ownership for the rubber hand. Together these results suggest that the integration of proprioceptive information with cues for arm position derived from the illusory context differs between individuals partly in relation to traits associated with ASD. We suggest that the observed differences in sensory integration can be best explained in terms of differing expectations regarding the precision of sensory estimates in contexts that suggest uncertainty.

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...

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.

Cognitive neuroscience aspires to explain how the brain produces conscious states. Many people think this aspiration is threatened by the subjective nature of introspective reports, as well as by certain philosophical arguments. We propose that good neuroscientific explanations of conscious states can consolidate an interpretation of introspective reports, in spite of their subjective nature. This is because the relative quality of explanations can be evaluated on independent, methodological grounds. To illustrate, we review studies that suggest that aspects of the feeling of being in control of one's bodily movement can be explained in terms of the complex and surprising way the brain predicts movement. This is a modest type of functional, contrastive explanation. Though we do not refute the threatening philosophical arguments, we show that they do not apply to this type of explanation.

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

The theory of rationality has traditionally been concerned with the investigation of the norms of rational thought and behaviour, and with the reasoning pro‐cedures that satisfy them. As a consequence, the investigation of irrationality has largely been restricted to the behaviour or thought that violates these norms. There are, how‐ever, other forms of irrationality. Here we propose that the delusions that occur in schizophrenia constitute a paradigm of irrationality. We examine a leading theory of schizophrenic delusion and propose that some delusions can be traced to a violation of a condition on thought we call egocentricity. We argue that the violation of egocen‐tricity leads to irrational states that cannot be explained by the traditional categories of irrationality and conclude, therefore, that these states belong in a new branch of the theory of irrationality, that of experiential irrationality.

It appears that consciousness science is progressing soundly, in particular in its search for the neural correlates of consciousness. There are two main approaches to this search, one is content-based (focusing on the contrast between conscious perception of, e.g., faces vs. houses), the other is state-based (focusing on overall conscious states, e.g., the contrast between dreamless sleep vs. the awake state). Methodological and conceptual considerations of a number of concrete studies show that both approaches are problematic: the content-based approach seems to set aside crucial aspects of consciousness; and the state-based approach seems over-inclusive in a way that is hard to rectify without losing sight of the crucial conscious-unconscious contrast. Consequently, the search for the neural correlates of consciousness is in need of new experimental paradigms.

Crispin Wright has sought to establish the possibility of ‘significant metaphysics’ in the shape of a common metric with which to measure the realism or robustness of various discourses. One means by which to place discourses in the metric is via the ‘cognitive command constraint’. Importantly, this constraint must be a priori. Richard Rorty has argued against this, that, given content is a function of standards of representationality, the a priori requirement cannot be satisfied. I show that this attack is inconsistent: to run his own argument Rorty must take recourse to a idealized view of identification of discourses which conflicts with his own basic premise about the determination of content. Hence Rorty’s argument should not lead us to conclude that significant metaphysics is impossible

The normative character of meaning creates deep problems for the attempt to give a reductive explanation of the constitution of meaning. I identify and critically examine an increasingly popular Carnap-style position, which I call Internalized Meaning Factualism (versions of which I argue are defended by, e.g., Robert Brandom, Paul Horwich and Huw Price), that promises to solve the problems. According to this position, the problem of meaning can be solved by prohibiting an external perspective on meaning constituting properties. The idea is that if we stick to a perspective on meaning that is internal to meaning discourse, then we can preserve the normativity of meaning and yet locate meaning in the natural world. I develop a generic motivation for this position, but argue that, since this motivation is consistent with the Ramsey–Carnap–Lewis–Jackson reductionist strategy, internalized meaning factualism is unstable. The problems about the normativity of meaning can therefore not be sidestepped in this way.

Three challenges to a unified understanding of delusions emerge from Radden's On Delusion (2011). Here, I propose that in order to respond to these challenges, and to work towards a unifying framework for delusions, we should see delusions as arising in inference under uncertainty. This proposal is based on the observation that delusions in key respects are surprisingly like perceptual illusions, and it is developed further by focusing particularly on individual differences in uncertainty expectations

Consciousness. We have come to expect science to be able to explain all sorts of phenomena in the world (global warming, hereditary diseases, life – you name it). Consciousness is an anomaly in the success story of science for there is a real question whether science, in particular neuroscience, can explain much about what consciousness is. A good question to ask is how and to what extent consciousness resists scientific explanation. That might tell us something about what is special about consciousness.

An exciting theory in neuroscience is that the brain is an organ for prediction error minimization. This theory is rapidly gaining influence and is set to dominate the science of mind and brain in the years to come. PEM has extreme explanatory ambition, and profound philosophical implications. Here, I assume the theory, briefly explain it, and then I argue that PEM implies that the brain is essentially self-evidencing. This means it is imperative to identify an evidentiary boundary between the brain and its environment. This boundary defines the mind-world relation, opens the door to skepticism, and makes the mind transpire as more inferentially secluded and neurocentrically skull-bound than many would nowadays think. Therefore, PEM somewhat deflates contemporary hypotheses that cognition is extended, embodied and enactive; however, it can nevertheless accommodate the kinds of cases that fuel these hypotheses.