Hallucinations as intensified forms of mind-wandering

This paper argues for a novel way of thinking about hallucinations as intensified forms of mind-wandering. Starting from the observation that hallucinations are associated with hyperactive sensory areas underlying the content of hallucinatory experiences and a confusion with regard to the reality of the source of these experiences, the paper first reviews the different factors that might contribute to the impairment of reality monitoring. The paper then focuses on the sensory characteristics determining the vividness of an experience, reviews their relationship to the sensory hyperactivity observed in hallucinations, and investigates under what circumstances they can drive reality judgements. Finally, based on these considerations, the paper presents its main proposal according to which hallucinations are intensified forms of mind-wandering that are amplified along their sensory characteristics, and sketches a possible model of what factors might determine if an internally and involuntarily generated perceptual representation is experienced as a hallucination or as an instance of mind-wandering. This article is part of the theme issue ‘Offline perception: voluntary and spontaneous perceptual experiences without matching external stimulation’.

Cognitive Flexibility for Semantic and Perceptual Information in Developmental Stuttering

Purpose The purpose of this study was to examine cognitive flexibility for semantic and perceptual information in preschool children who stutter (CWS) and who do not stutter (CWNS). Method Participants were 44 CWS and 44 CWNS between the ages of 3;0 and 5;11 (years;months). Cognitive flexibility was measured using semantic and perceptual categorization tasks. In each task, children were required to match a target object with two different semantic or perceptual associates. Main dependent variables were reaction time and accuracy. Results The accuracy with which CWS and CWNS shifted between one semantic and perceptual representation to another was similar, but the CWS did so significantly more slowly. Both groups of children had more difficulty switching between perceptual representations than semantic ones. Conclusion CWS are less efficient (slower), though not less accurate, than CWNS in their ability to switch between different representations in both the verbal and nonverbal domains.

The Impoverished Representations of Brains in Vats

In this article, the notion that brains in vats with perceptual experiences of the same type as ours could perceptually represent other entities than shapes is challenged. Whereas it is often held that perceptual experiences with the same phenomenal character as ours could represent computational properties, the present author argues that this is not the case for shapes. His argument is in brief that the phenomenal character of a normal visual experience exemplifies shapes – phenomenal shapes – which functions as the vehicle for our perceptual representation of shapes. Due to the unique mereological structure of shapes, phenomenal shapes are unable to reliably track any property but shapes. In so far as reliable tracking is a necessary condition for perceptual representation, phenomenal shapes can consequently and contrary to received wisdom only represent shapes.

Conceptual rather than perceptual similarity enables generalization across perceptually different appearances of familiarized faces

Face recognition is a challenging categorization task, as in many cases the variability between different images of the same identity may be larger than the variability between images of different identities. Nevertheless, humans excel in this task, in particular for faces they are familiar with. What type of learning and what is the nature of the representation of the learned identity that support such remarkable categorization ability? Here we propose that conceptual learning and the generation of a conceptual representation of the learned identity in memory enables this classification performance. First, we show that humans learn to link perceptually different faces to the same identity, if faces are learned with the same conceptual information. Next, we show that this conceptual learning does not generate a single perceptual representation of the different appearances of each identity. Instead, perceptually dissimilar images of the same identity remain separated in the perceptual space and are linked conceptually rather than perceptually. This conceptual representation of face identity is advantageous, as it enables generalization across perceptually dissimilar images of the same identity/category, without increasing false recognition of perceptually similar images of different identities. A similar conceptual mechanism may also apply to other familiar categories such as familiar voices or objects of expertise that involve fine discrimination of a homogenous sets of stimuli that are linked to unique conceptual information. Overall these findings highlight the importance of studying the contribution of both cognition and perception to face recognition.

Content and the Explanatory Role of Experience

It is widely held both that having certain sorts of perceptual experiences can explain one’s ability to have certain sorts of thoughts and that we can use this fact to show that perception and thought differ in certain fundamental ways. Some hold that the explanatory role of experience shows that experiences, unlike thoughts, are not contentful states; others hold that it shows that experiences, unlike thoughts, are nonconceptual. The chapter argues that these theses can’t be established by arguments based on premises requiring experience to play certain explanatory roles. It considers three arguments of this form, which appeal, respectively, to the requirements that experience explain our capacity for singular thought, that it explain the reference of certain demonstrative concepts, and that it explain our ability to learn new concepts. In section 4, it argues that the explanatory role of experience can help decide questions about scope of perceptual representation.

Adaptation aftereffects reveal how categorization training changes the encoding of face identity

Previous research suggests that learning to categorize faces along a novel dimension changes the perceptual representation of such dimension, increasing its discriminability, its invariance, and the information used to identify faces varying along the dimension. A common interpretation of these results is that categorization training promotes the creation of novel dimensions, rather than simply the enhancement of already-existing representations. Here, we trained a group of participants to categorize faces that varied along two morphing dimensions, one of them relevant to the categorization task and the other irrelevant to the task. An untrained group did not receive such categorization training. In three experiments, we used face adaptation aftereffects to explore how categorization training changes the encoding of face identities at the extremes of the category-relevant dimension, and whether such training produces encoding of the category-relevant dimension as a preferred direction in face space. The pattern of results suggests that categorization training enhances the already-existing norm-based coding of face identity, rather than creating novel category-relevant representations. We formalized this conclusion in a model that explains the most important results in our experiments and serves as a working hypothesis for future work in this area.