Body-scaled affordances in sensory substitution

The research field on sensory substitution devices has strong implications for theoretical work on perceptual consciousness. One of these implications concerns the extent to which the devices allow distal attribution. The present study applies a classic empirical approach on the perception of affordances to the field of sensory substitution. The reported experiment considers the perception of the stair-climbing affordance. Participants judged the climbability of steps apprehended through a vibrotactile sensory substitution device. If measured with standard metric units, climbability judgments of tall and short participants differed, but if measured in units of leg length, judgments did not differ. These results are similar to paradigmatic results in regular visual perception. We conclude that our sensory substitution device allows the perception of affordances. More generally, we argue that the theory of affordances may enrich theoretical debates concerning sensory substitution to a larger extent than has hitherto been the case.     

Sensory substitution: an approach to the experimental study of perception / Sustitución sensorial: un abordaje para el estudio experimental de la percepción

Abstract

Sensory substitution refers to the phenomenon where object and environment information normally acquired through one sense can be obtained by another sense. For example, visual input being provided by hearing or touching. Sensory substitution devices are technological designs that transform the characteristics of one sensory modality into stimuli of another sensory modality. These devices were developed with two purposes: (1) to assist people with sensory disabilities in daily tasks; and (2) to study the involved mechanisms of brain plasticity. This article reviews studies in which sensory substitution phenomenon is employed as a methodological strategy to study visual perception. Furthermore, its use is discussed as an experimental platform to contrast new perceptual theories and underlying neurophysiological mechanisms that are currently under review.     

Perceptual interactions in a minimalist virtual environment

How in real-life or through the use of technical devices can we recognize the presence of other persons and under what conditions can we differentiate them from objects? In order to approach this question, in the study reported here we explored the most basic conditions necessary for participants to recognize the presence of another person during a perceptual interaction. We created a mini-network of two minimalist devices and investigated whether participants were able to differentiate the perception of another person from the perception of a fixed and a mobile object even when the pattern of sensory stimulation was reduced to a bare minimum. We show that participants can recognize when the all-or-none tactile stimulation they experienced was attributable to an encounter with the other participant's avatar or the mobile object rather than with a fixed object. Participants were also able to establish different strategies in order to favor the situations of mutual perception. Thus, in the minimalist conditions of our experiment, the perception of another intentional subject was not based purely on any particular shape or objective trajectories of displacement; it was also based on properties that are intrinsic to the joint perceptual activity itself.     

Potential perceptual bases for successful use of a vibrotactile speech perception aid

This paper examines the possibility that perception of vibrotactile speech stimuli is enhanced in adults with early and life-long use of hearing aids. We present evidence that vibrotactile aid benefit in adults is directly related to the age at which the hearing aid was fitted and the duration of its use. The stimulus mechanism responsible for this effect is hypothesized to be long-term vibrotactile stimulation by high powered hearing aids. We speculate on possible mechanisms for enhanced vibrotactile speech perception as the result of hearing aid use: (1) long-term experience receiving degraded or impoverished speech stimuli results in a speech processing system that is more effective for novel stimuli, independent of perceptual modality; and/or (2) long-term sensory/perceptual experience causes neural changes that result in more effective delivery of speech information via somatosensory pathways.     

Vertical-horizontal illusion present for sighted but not early blind humans using auditory substitution of vision

This experiment was undertaken to investigate the effect of sensory modality (vision vs. audition) and of visual status (early blind vs. sighted) on susceptibility to the vertical-horizontal illusion. Early blind volunteers and blindfolded sighted subjects explored variants of the vertical-horizontal illusion using a device that substituted audition for vision, whereas sighted subjects from an independent group inspected the same stimuli visually. Sensitivity to the vertical-horizontal illusion, including an illusion of moderate strength when using the sensory substitution device, was observed only in the two sighted groups. The existence of an illusion effect when using such a device supports the idea of a visual perception provided by sensory substitution, whereas the attenuation of the vertical-horizontal illusion strength is consistent with the visual field shape theory (Künnapas, 1955a). The absence of the illusion effect in early blind subjects suggests that the sensory experience influences the nature of perception and that the visual experience plays a crucial role in the vertical-horizontal illusion, in accordance with the size-constancy scaling theory (Gregory, 1963).     

The case for proprioception

In formulating a theory of perception that does justice to the embodied and enactive nature of perceptual experience, proprioception can play a valuable role. Since proprioception is necessarily embodied, and since proprioceptive experience is particularly integrated with one’s bodily actions, it seems clear that proprioception, in addition to, e.g., vision or audition, can provide us with valuable insights into the role of an agent’s corporal skills and capacities in constituting or structuring perceptual experience. However, if we are going to have the opportunity to argue from analogy with proprioception to vision, audition, touch, taste, or smell, then it is necessary to eschew any doubts about the legitimacy of proprioception’s inclusion into the category of perceptual modalities. To this end, in this article, I (1) respond to two arguments that Shaun Gallagher (2003) presents in “Bodily self-awareness and objectperception” against proprioception’s ability to meet the criteria of object perception, (2) present a diagnosis of Gallagher’s position by locating a misunderstanding in the distinction between proprioceptive information and proprioceptive awareness, and (3) show that treating proprioception as a perceptual modality allows us to account for the interaction of proprioception with the other sensory modalities, to apply the lessons we learn from proprioception to the other sensory modalities, and to account for proprioceptive learning. Finally, (4) I examine Sydney Shoemaker’s (1994) identification constraint and suggest that a full-fledged notion of object-hood is unnecessary to ground a theory of perception.     

Amodal completion and relationalism

Amodal completion is usually characterized as the representation of those parts of the perceived object that we get no sensory stimulation from. In the case of the visual sense modality, for example, amodal completion is the representation of occluded parts of objects we see. I argue that relationalism about perception, the view that perceptual experience is constituted by the relation to the perceived object, cannot give a coherent account of amodal completion. The relationalist has two options: construe the perceptual relation as the relation to the entire perceived object or as the relation to the unoccluded parts of the perceived object. I argue that neither of these options are viable.

     

The self in action effects: selective attenuation of self-generated sounds

The immediate experience of self-agency, that is, the experience of generating and controlling our actions, is thought to be a key aspect of selfhood. It has been suggested that this experience is intimately linked to internal motor signals associated with the ongoing actions. These signals should lead to an attenuation of the sensory consequences of one’s own actions and thereby allow classifying them as self-generated. The discovery of shared representations of actions between self and other, however, challenges this idea and suggests similar attenuation of one’s own and other’s sensory action effects.Here, we tested these assumptions by comparing sensory attenuation of self-generated and observed sensory effects. More specifically, we compared the loudness perception of sounds that were either self-generated, generated by another person or a computer. In two experiments, we found a reduced perception of loudness intensity specifically related to self-generation. Furthermore, the perception of sounds generated by another person and a computer did not differ from each other. These findings indicate that one’s own agentive influence upon the outside world has a special perceptual quality which distinguishes it from any sort of external influence, including human and non-human sources. This suggests that a real sense of self-agency is not a socially shared but rather a unique and private experience.     

ARE EMOTIONS PERCEPTUAL EXPERIENCES OF VALUE?

A number of emotion theorists hold that emotions are perceptions of value. In this paper I say why they are wrong. I claim that in the case of emotion there is nothing that can provide the perceptual modality that is needed if the perceptual theory is to succeed (where by ‘perceptual modality’ I mean the particular manner in which something is perceived). I argue that the five sensory modalities are not possible candidates for providing us with ‘emotional perception’. But I also say why the usual candidate offered – namely feeling or affectivity – does not give us the sought‐after perceptual modality. I conclude that as there seems to be nothing else that can provide the needed perceptual modality, we should reject the perceptual theory of emotion. 1     

"Binaural rivalry": dichotic listening as a tool for the investigation of the neural correlate of consciousness

Since about two decades neuroscientists have systematically faced the problem of consciousness: the aim is to discover the neural activity specifically related to conscious perceptions, i.e. the biological properties of what philosophers call qualia. In this view, a neural correlate of consciousness (NCC) is a precise pattern of brain activity that specifically accompanies a particular conscious experience. Almost all studies aimed at investigating the NCC have been carried out in the visual system. One of the most promising paradigms is based on sensory stimuli which elicit bistable percepts, as they allow to decouple subjective perception from the characteristics of the physical stimulation. Such kind of perception can be produced in the visual modality by using particular images (e.g. Rubin's vase/face figure) or by presenting two dissimilar stimuli separately to the two eyes (binocular rivalry). The stimuli compete for perceptual dominance and each image is visible in turn for a few seconds, while the other is suppressed. The use of this methodology has led to important findings concerning visual consciousness, which are briefly discussed. For the investigation of auditory consciousness, a similar stimulation paradigm can be achieved by using dichotic listening, consisting in two different stimuli presented each to one ear, which compete for perception (binaural rivalry). The principal aim of the present mini-review is to discuss the few contributes facing the issue of auditory consciousness and to advance the use of dichotic listening and binaural rivalry as valid tools for its investigation.     

A perception theory in mind–body medicine: guided imagery and mindful meditation as cross-modal adaptation

A new theory of mind–body interaction in healing is proposed based on considerations from the field of perception. It is suggested that the combined effect of visual imagery and mindful meditation on physical healing is simply another example of cross-modal adaptation in perception, much like adaptation to prism-displaced vision. It is argued that psychological interventions produce a conflict between the perceptual modalities of the immune system and vision (or touch), which leads to change in the immune system in order to realign the modalities. It is argued that mind–body interactions do not exist because of higher-order cognitive thoughts or beliefs influencing the body, but instead result from ordinary interactions between lower-level perceptual modalities that function to detect when sensory systems have made an error. The theory helps explain why certain illnesses may be more amenable to mind–body interaction, such as autoimmune conditions in which a sensory system (the immune system) has made an error. It also renders sensible erroneous changes, such as those brought about by “faith healers,” as conflicts between modalities that are resolved in favor of the wrong modality. The present view provides one of very few psychological theories of how guided imagery and mindfulness meditation bring about positive physical change. Also discussed are issues of self versus non-self, pain, cancer, body schema, attention, consciousness, and, importantly, developing the concept that the immune system is a rightful perceptual modality. Recognizing mind–body healing as perceptual cross-modal adaptation implies that a century of cross-modal perception research is applicable to the immune system.     

An Information Space for Partial Length Perception in Dynamic Touch

Two experiments evaluated change in the perception of an environmental property (object length) in each of 3 perceptual modalities (vision, audition, and haptics) when perceivers were provided with the opportunity to experience the same environmental property by means of an additional perceptual modality (e.g., haptics followed by vision, vision followed by audition, or audition followed by haptics). Experiment 1 found that (a) posttest improvements in perceptual consistency occurred in all 3 perceptual modalities, regardless of whether practice included experience in an additional perceptual modality and (b) posttest improvements in perceptual accuracy occurred in haptics and audition but only when practice included experience in an additional perceptual modality. Experiment 2 found that learning curves in each perceptual modality could be accommodated by a single function in which auditory perceptual learning occurred over short time scales, haptic perceptual learning occurred over middle time scales, and visual perceptual learning occurred over long time scales. Analysis of trial-to-trial variability revealed patterns of long-term correlations in all perceptual modalities regardless of whether practice included experience in an additional perceptual modality.     

Frege's Puzzle for Perception

According to an influential variety of the representational view of perceptual experience—the singular content view—the contents of perceptual experiences include singular propositions partly composed of the particular physical object(s) a given experience is about or of. The singular content view faces well‐known difficulties accommodating hallucinations; I maintain that there is also an analogue of Frege's puzzle that poses a significant problem for this view. In fact, I believe that this puzzle presents difficulties for the theory that are unique to perception in that strategies that have been developed to respond to Frege's puzzle in the case of belief cannot be employed successfully in the case of perception. Ultimately, I maintain that this perceptual analogue of Frege's puzzle provides a compelling reason to reject the singular content view of perceptual experience.     

The perception of space and form recognition in a simulated environment: the case of minimalist sensory-substitution devices

Whenever we explore a simulated environment, the sensorimotor interactions that underlie our perception of space may be modified. We investigated the conditions under which it is possible to acquire the mastery of new sensorimotor laws and thereby to infer new perceptual spaces. A computer interface, based on the principles of minimalist sensory-substitution devices, was designed to enable different possible links between a user's actions (manipulation of a mouse and/or keys of a keyboard) and the resulting pattern of sensory stimulation (visual or auditory) to be established. The interface generated an all-or-none stimulus whose activation varied as a function of the participant's exploration of a hidden form. In this study we addressed the following questions: What are the conditions necessary for participants to understand their actions as constituting a displacement in a simulated space? What are the conditions required for participants to conceive of sensations as originating from the encounter with an object situated in this space? Finally, what are the conditions required for participants to recognise forms within this space? The results of the two experiments reported here show that, under certain conditions, participants can interpret the new sensorimotor laws as movements in a new perceptual space and can recognise simple geometric forms, and that this occurs no matter whether the sensory stimulation is presented in the visual or auditory modality.     

Sensory substitution and the human-machine interface

Recent advances in the instrumentation technology of sensory substitution have presented new opportunities to develop systems for compensation of sensory loss. In sensory substitution (e.g. of sight or vestibular function), information from an artificial receptor is coupled to the brain via a human-machine interface. The brain is able to use this information in place of that usually transmitted from an intact sense organ. Both auditory and tactile systems show promise for practical sensory substitution interface sites. This research provides experimental tools for examining brain plasticity and has implications for perceptual and cognition studies more generally.     

The epistemic force of perceptual experience

What is the metaphysical nature of perceptual experience? What evidence does experience provide us with? These questions are typically addressed in isolation. In order to make progress in answering both questions, perceptual experience needs to be studied in an integrated manner. I develop a unified account of the phenomenological and epistemological role of perceptual experience, by arguing that sensory states provide perceptual evidence due to their metaphysical structure. More specifically, I argue that sensory states are individuated by the perceptual capacities employed and that there is an asymmetric dependence between their employment in perception and their employment in hallucination and illusion. Due to this asymmetric dependence, sensory states provide us with evidence.     

Sellars and Nonconceptual Content

In this paper I take up the question of whether Wilfrid Sellars has a notion of non‐conceptual perceptual content. The question is controversial, being one of the fault lines along which so‐called left and right Sellarsians diverge. In the paper I try to make clear what it is in Sellars' thought that leads interpreters to such disparate conclusions. My account depends on highlighting the importance of Sellars' little discussed thesis that perception involves a systematic form of mis‐categorization, one where perceivers mistake their sensory states to be properties of physical objects. I argue that the counterpart color and shape attributes of these states, which become ‘point of viewish’ when organized by the productive imagination, provides perceptual experience with its non‐conceptual representational content. I then argue that this content is not a form of the mythical Given because one can only have a non‐conceptual point of view on an object when an object is introduced into one's perceptual experience through the conceptual mis‐taking of one's sensory states. So, while Sellars has a notion of non‐conceptual representational content, it can only be salient in the context of a perceptual act that is conceptual overall.     

Action-dependent perceptual invariants: from ecological to sensorimotor approaches

Ecological and sensorimotor theories of perception build on the notion of action-dependent invariants as the basic structures underlying perceptual capacities. In this paper we contrast the assumptions these theories make on the nature of perceptual information modulated by action. By focusing on the question, how movement specifies perceptual information, we show that ecological and sensorimotor theories endorse substantially different views about the role of action in perception. In particular we argue that ecological invariants are characterized with reference to transformations produced in the sensory array by movement: such invariants are transformation-specific but do not imply motor-specificity. In contrast, sensorimotor theories assume that perceptual invariants are intrinsically tied to specific movements. We show that this difference leads to different empirical predictions and we submit that the distinction between motor equivalence and motor-specificity needs further clarification in order to provide a more constrained account of action/perception relations.     

Achieving Transparency: An Argument For Enactivism

The transparency of perceptual experience has been invoked in support of many views about perception. I argue that it supports a form of enactivism—the view that capacities for perceptual experience and for intentional agency are essentially interdependent. I clarify the perceptual phenomenon at issue, and argue that enactivists should expect to find a parallel instance of transparency in our agentive experience, and that the two forms of transparency are constitutively interdependent (Section 1). I then argue that i) we do indeed find such parallels: the way in which an action is directed towards its goal through our bodily movements parallels the way in which an experience is directed towards its object through our perceptual sensation (Section 2), and ii) reflecting on sensorimotor skills shows why the two instances of transparency are constitutively interdependent (Section 3). Section 4 gives reasons for generalizing beyond the cases considered so far by applying the enactive view to Kohler's landmark studies of perceptual adaptation. The final section clarifies the form of enactivism to which the previous sections point. The view that emerges is one whereby our perceptual and practical skills are interrelated aspects of a single capacity to have one's mind intentionally directed upon the world. The transparency of experience, on this view, is achieved in virtue of our capacities as agents as much as it is given in virtue of our capacities as perceivers.     

About the time-shrinking illusion in the tactile modality

The aim of this study was to examine the occurrence of a so-called time-shrinking illusion in the tactile modality, while it had been tested so far mainly with auditory and visual stimuli. We examined whether the perception of an empty time interval marked by two brief tactile stimuli, S (240 ms), would be influenced by the presence of a preceding time interval, P (160, 240, or 320 ms). Results showed that S was underestimated when P was shorter than S. This underestimation appeared as a kind of perceptual assimilation between P and S, but S was not overestimated when P was longer. The underestimation was rather interpreted as a manifestation of the time-shrinking illusion.