Jakob Hohwy

The effect of the body transfer illusion on the perceived strength of self- and externally-generated “tickle” sensations was investigated. As expected, externally generated movement produced significantly higher ratings of tickliness than those associated with self-generated movements. Surprisingly, the body transfer illusion had no influence on the ratings of tickliness, suggesting that highly surprising, and therefore hard to predict, experiences of body image and first-person perspective do not abolish the attenuation of tickle sensations. In addition, evidence was found that a version of the rubber hand illusion exists within the body transfer illusion. We situate our findings within the larger debate over sensory attenuation: there is an attenuation of prediction errors that depends upon the context in which sensory input is predicted , and sensory attenuation is a necessary consequence of self-generated movement irrespective of context . The results support the notion of active inference

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.

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

There is a view on consciousness that has strong intuitive appeal and empirical support: the intermediate-level theory of consciousness, proposed mainly by Ray Jackendoff and by Jesse Prinz. This theory identifies a specific “intermediate” level of representation as the basis of human phenomenal consciousness, which sits between high-level non-perspectival thought processes and low-level disjointed feature-detection processes in the perceptual and cognitive processing hierarchy. In this article, we show that the claim that consciousness arises at an intermediate-level is true of some cognitive systems, but only in virtue of specific constraints on their active interactions with the environment. We provide ecological reasons for why certain processing levels in a cognitive hierarchy are privileged with respect to consciousness. We do this from the perspective of a prediction-error minimization model of perception and cognition, relying especially on the notion of active inference: the privileged level for consciousness depends on the specific dispositions of an organism concerned with inferring its policies for action. Such a level is indeed intermediate for humans, but this depends on the spatiotemporal resolution of the typical actions that a human organism can normally perform. Thus, intermediateness is not an essential feature of consciousness. In organisms with different action dispositions the privileged level or levels may differ as well.

Among all their sensations, agents need to distinguish between those caused by themselves and those caused by external causes. The ability to infer agency is particularly challenging under conditions of uncertainty. Within the predictive processing framework, this should happen through active control of prediction error that closes the action-perception loop. Here we use a novel, temporally-sensitive, behavioural proxy for prediction error to show that it is minimised most quickly when volatility is high and when participants report agency, regardless of the accuracy of the judgement. We demonstrate broad effects of uncertainty on accuracy of agency judgements, movement, policy selection, and hypothesis switching. Measuring autism traits, we find differences in policy selection, sensitivity to uncertainty and hypothesis switching despite no difference in overall accuracy.

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...

This essay reflects upon certain aspects of Wittgenstein's own practices as a teacher. Doing philosophy always took priority for Wittgenstein, whether this was in oral or written form: it was important to show the deep puzzles in our language as a step toward dissolving them. In this respect, one can teach only as a guide; it is a matter of showing more than saying. Wittgenstein's approach suggests a model that I will call tacit teaching. Tacit teaching refers to the many forms of informal instruction—some intentional, some unintentional, and some difficult to categorize simply as one or the other—by which skills, capacities, and dispositions are passed along within a domain of practice. Wittgenstein repeatedly uses the language of signposts, of wandering through a city, of being lost and finding one's way, of needing a guide, of learning how to go on by one's self, to refer to the complex web of knowledge and understanding that allows successful autonomous practice in some discipline: most pertinently, in the context of Wittgenstein's own teaching and writing, the discipline of doing philosophy, but with clear reference to teaching and learning in other complex and ill‐structured domains as well.

The effect of the body transfer illusion on the perceived strength of self- and externally-generated “tickle” sensations was investigated. As expected, externally generated movement produced significantly higher ratings of tickliness than those associated with self-generated movements. Surprisingly, the body transfer illusion had no influence on the ratings of tickliness, suggesting that highly surprising, and therefore hard to predict, experiences of body image and first-person perspective do not abolish the attenuation of tickle sensations. In addition, evidence was found that a version of the rubber hand illusion exists within the body transfer illusion. We situate our findings within the larger debate over sensory attenuation: there is an attenuation of prediction errors that depends upon the context in which sensory input is predicted, and sensory attenuation is a necessary consequence of self-generated movement irrespective of context. The results support the notion of active inference.

In previous research on the evaluation of food images, we found that appetitive food images were rated higher following a positive prediction than following a negative prediction, and vice versa for aversive food images. The findings suggested an active confirmation bias. Here, we examine whether this influence from prediction depends on the evaluative polarization of the food images. Specifically, we divided the set of food images into "strong" and "mild" images by how polarized (i.e., extreme) their average ratings were across all conditions. With respect to the influence from prediction, we raise two alternative hypotheses. According to a predictive dissonance hypothesis, the larger the discrepancy between prediction and outcome, the stronger the active inference toward accommodating the outcome with the prediction; thus, the confirmation bias should obtain particularly with strong images. Conversely, according to a nudging-in-volatility hypothesis, the active confirmation bias operates only on images within a dynamic range, where the values of images are volatile, and not on the evaluation of images that are too obviously appetitive or aversive; accordingly, the effects from prediction should occur predominately with mild images. Across the data from two experiments, we found that the evaluation of mild images tended to exhibit the confirmation bias, with ratings that followed the direction given by the prediction. For strong images, there was no confirmation bias. Our findings corroborate the nudging-in-volatility hypothesis, suggesting that predictive cues may be able to tip the balance of evaluation particularly for food images that do not have a strongly polarized value.

This chapter focuses on what’s novel in the perspective that the prediction error minimization (PEM) framework affords on the cognitive-scientific project of explaining intelligence by appeal to internal representations. It shows how truth-conditional and resemblance-based approaches to representation in generative models may be integrated. The PEM framework in cognitive science is an approach to cognition and perception centered on a simple idea: organisms represent the world by constantly predicting their own internal states. PEM theories often stress the hierarchical structure of the generative models they posit. The novel explanatory power of the PEM account derives largely from the way in which pairs of generative and recognition models interact. “Predictive coding” refers to an encoding strategy in which predicted portions of an input signal are subtracted from the actual signal received, so that only the difference between the two is passed as output to the next stage of information processing.