Sensory substitution devices provide through an unusual sensory modality (the substituting modality, e.g., audition) access to features of the world that are normally accessed through another sensory modality (the substituted modality, e.g., vision). In this article, we address the question of which sensory modality the acquired perception belongs to. We have recourse to the four traditional criteria that have been used to define sensory modalities: sensory organ, stimuli, properties, and qualitative experience (Grice, 1962), to which we have added the criteria (...) of behavioral equivalence (Morgan, 1977), dedication (Keeley, 2002), and sensorimotor equivalence (O’Regan & Noe¨, 2001). We discuss which of them are fulfilled by perception through sensory substitution devices and whether this favors the view that perception belongs to the substituting or to the substituted modality. Though the application of a number of criteria might be taken to point to the conclusion that perception with a sensory substitution device belongs to the substituted modality, we argue that the evidence leads to an alternative view on sensory substitution. According to this view, the experience after sensory substitution is a transformation, extension, or augmentation of our perceptual capacities, rather than being something equivalent or reducible to an already existing sensory modality. We develop this view by comparing sensory substitution devices to other ‘‘mind-enhancing tools’’ such as pen and paper, sketchpads, or calculators. An analysis of sensory substitution in terms of mind-enhancing tools unveils it as a thoroughly transforming perceptual experience and as giving rise to a novel form of perceptual interaction with the environment. (shrink)

Molyneux’s question asks whether someone born blind, who could distinguish cubes from spheres using his tactile sensation, could recognize those objects if he received his sight. Locke says no: the newly sighted person would fail to point to the cube and call it a cube. Locke never provided a complete explanation for his negative response, and there are concerns of inconsistency with other important aspects of his theory of ideas. These charges of inconsistency rest upon an unrecognized and unfounded assumption (...) that seeing entails recognition. Locke’s negative answer to Molyneux’s question is consistent with his other philosophical commitments. (shrink)

To what extent is the external world the way that it appears to us in perceptual experience? This perennial question in philosophy is no doubt ambiguous in many ways. For example, it might be taken as equivalent to the question of whether or not the external world is the way that it appears to be? This is a question about the epistemology of perception: Are our perceptual experiences by and large veridical representations of the external world? Alternatively, the question might (...) be taken as asking whether or not the external world is like its ways of appearing to us, where the expression “ways of appearing” is intended to pick out aspects of our perceptual experiences themselves. This is a metaphysical version of the question of the relationship between appearance and reality: What is the relationship between the phenomenal features that characterize perceptual experience, on the one hand, and the mind-independent features of the external objects of perception, on the other? There are some philosophers who might resist distinguishing between these two questions. For them, “ways of appearing” in the phenomenal sense just are the ways that things appear to be (let’s call the latter the “intentional sense” of “ways of appearing”).1 That is, the phenomenal character of an experience is nothing over and above its representational content. Phenomenal properties are represented properties—the properties that an experience attributes to the external objects of perception. The question of whether or not phenomenal properties can be identified with the represented properties of an experience mirrors traditional questions in the philosophy of perception. If they can be identified with each other, then in veridical perception we might be said to “directly grasp” features of the external world through perception. The properties that are present to the mind are the very same properties that belong to the external objects of perception. Such a view affords.... (shrink)

The posterior parietal cortex (PPC) is the most likely site where egocentric spatial relationships are represented in the brain. PPC cells receive visual, auditory, somaesthetic, and vestibular sensory inputs; oculomotor, head, limb, and body motor signals; and strong motivational projections from the limbic system. Their discharge increases not only when an animal moves towards a sensory target, but also when it directs its attention to it. PPC lesions have the opposite effect: sensory inattention and neglect. The PPC does not seem (...) to contain a “map” of the location of objects in space but a distributed neural network for transforming one set of sensory vectors into other sensory reference frames or into various motor coordinate systems. Which set of transformation rules is used probably depends on attention, which selectively enhances the synapses needed for making a particular sensory comparison or aiming a particular movement. (shrink)

The parietal cortex is divided into two major functional regions: the anterior parietal cortex that includes primary somatosensory cortex, and the posterior parietal cortex (PPC) that includes the rest of the parietal lobe. The PPC contains multiple representations of space. In Dijkerman & de Haan's (D&dH's) model, higher spatial representations are separate from PPC functions. This model should be developed further so that the functions of the somatosensory system are integrated with specific functions within the PPC and higher spatial representations. (...) Through this further specification of the model, one can make better predictions regarding functional interactions between somatosensory and visual systems. (shrink)

Intentionalism is the view that the phenomenal character of a conscious experience is wholly determined by, or even reducible to, its representational content. In this essay I put forward a version of intentionalism that allows (though does not require) the reduction of phenomenal character to representational content. Unlike other reductionist theories, however, it does not require the acceptance of phenomenal externalism (the view that phenomenal character does not supervene on the internal state of the subject). According the view offered here, (...) phenomenal characters essentially represent subject-environment relations that are relevant to the possibilities for causal interaction between the subject and the environment; relations of the kind that J. J. Gibson dubbed affordances. I argue for this view chiefly through an examination of spatial perception, though other cases are also considered. The view assumes that a phenomenal character has an essential functional role; though it need not be assumed that a functional role is sufficient for a phenomenal character. (shrink)

We like Euclidean geometry because we are men [sic], and have eyes and hands, and need to operate a concept of space that will be independent of orientation, distance and size. Lucas, A Treatise on Time and Space.

The paper proposes a way of bridging the gapbetween physical processes in the brain and the ''''felt''''aspect of sensory experience. The approach is based onthe idea that experience is not generated by brainprocesses themselves, but rather is constituted by theway these brain processes enable a particular form of''''give-and-take'''' between the perceiver and theenvironment. From this starting-point we are able tocharacterize the phenomenological differences betweenthe different sensory modalities in a more principledway than has been done in the past. We are also (...) ableto approach the issues of visual awareness andconsciousness in a satisfactory way. Finally weconsider a number of testable empirical consequences,one of which is the striking prediction of thephenomenon of ''''change blindness''''. (shrink)

Many current neurophysiological, psychophysical, and psychological approaches to vision rest on the idea that when we see, the brain produces an internal representation of the world. The activation of this internal representation is assumed to give rise to the experience of seeing. The problem with this kind of approach is that it leaves unexplained how the existence of such a detailed internal representation might produce visual consciousness. An alternative proposal is made here. We propose that seeing is a way of (...) acting. It is a particular way of exploring the environment. Activity in internal representations does not generate the experience of seeing. The out- side world serves as its own, external, representation. The experience of seeing occurs when the organism masters what we call the gov- erning laws of sensorimotor contingency. The advantage of this approach is that it provides a natural and principled way of accounting for visual consciousness, and for the differences in the perceived quality of sensory experience in the different sensory modalities. Sev- eral lines of empirical evidence are brought forward in support of the theory, in particular: evidence from experiments in sensorimotor adaptation, visual “filling in,” visual stability despite eye movements, change blindness, sensory substitution, and color perception. (shrink)

Reid offers an under-appreciated account of the primary/secondary quality distinction. He gives sound reasons for rejecting the views of Locke, Boyle, Galileo and others, and presents a better alternative, according to which the distinction is epistemic rather than metaphysical. Primary qualities, for Reid, are qualities whose intrinsic natures can be known through sensation. Secondary qualities, on the other hand, are unknown causes of sensations. Some may object that Reid's view is internally inconsistent, or unacceptably relativistic. However, a deeper understanding shows (...) that it is consistent, and relative only to normal humans. To acquire this deeper understanding, one must also explore the nature of dispositions, Reid's rejection of the theory of ideas, his distinction between sensation and perception, and his distinction between natural and acquired perceptions. (shrink)

Dijkerman & de Haan (D&dH) propose a somatosensory perceptual pathway that informs a consciously accessible body image, and an action pathway that provides information to a body schema, which is not consciously accessible. We argue that the body schema may become accessible to consciousness in some circumstances, possibly resulting from cross talk, but that this may be detrimental to skilled movement production.

It is widely accepted that physicalism faces its most serious challenge when it comes to making room for the phenomenal character of psychological experience, its so-called what-it-is-like aspect. The challenge has surfaced repeatedly over the past two decades in a variety of forms. In a particularly striking one, Frank Jackson considers a situation in which Mary, a brilliant scientist who knows all the physical facts there are to know about psychological experience, has spent the whole of her life in a (...) black and white room. He asks, What will happen when Mary is released from her black and white room or is given a colour television monitor? Will she learn anything or not? It seems just obvious that she will learn something about the world and our visual experience of it. But then it is inescapable that her previous knowledge was incomplete. But she had all the physical information. (Jackson 1986: 130). (shrink)

It is widely assumed that the art media can be individuated with reference to the sense modalities. Different art media are perceived by means of different sense modalities, and this tells us what properties of each medium are aesthetically relevant. The case of pictures appears to fit this principle well, for pictures are deemed purely and paradigmatically visual representations. However, recent psychological studies show that congenitally and early blind people have the ability to interpret and make raised‐line drawings through touch. (...) This shows that pictures are not essentially visual representations. The view that pictures are essentially visual follows from influential views of the nature of depiction and of the nature of vision that are mistaken. By rooting out the mistake, we learn something about pictures, something about vision, and something about the doctrine that art media are individuated by the sense modalities. (shrink)

After more than three centuries, Molyneux's question continues to challenge our understanding of cognition and perceptual systems. Locke, the original recipient of the question, approached it as a theoretical exercise relevant to long-standing philosophical issues, such as nativism, the possibility of common sensibles, and the empiricism-rationalism debate. However, philosophers were quick to adopt the experimentalist's stance as soon as they became aware of recoveries from congenital blindness through ophtalmic surgery. Such recoveries were widely reported to support empiricist positions, suggesting that (...) the question had found its empirical answer. Contrary to this common view, we argue that studies of patients recovering from early blindness through surgery cannot provide an answer. In fact, because of the very nature of such ophtalmological interventions it is impossible to test the question in the empirical conditions outlined by Molyneux. Thus we propose that Molyneux's question be treated as an early thought experiment of a specific kind. Although thought experiments of this kind cannot be turned into actual experimental conditions, they provide a conceptual restructuring of theories. Such restructuring in turn leads to new predictions that can then be tested by normal experiments. In accord with this interpretation, we show that Molyneux's question can be analyzed into a hierarchy of specific questions about vision in its phenomenal and sensory-motor components. Some of these questions do lead to actual experimental conditions that could be studied empirically. (shrink)

Sensory substitution devices (SSDs) aim to compensate for the loss of a sensory modality, typically vision, by converting information from the lost modality into stimuli in a remaining modality. “The vOICe” is a visual-to-auditory SSD which encodes images taken by a camera worn by the user into “soundscapes” such that experienced users can extract information about their surroundings. Here we investigated how much detail was resolvable during the early induction stages by testing the acuity of blindfolded sighted, naïve vOICe users. (...) Initial performance was well above chance. Participants who took the test twice as a form of minimal training showed a marked improvement on the second test. Acuity was slightly but not significantly impaired when participants wore a camera and judged letter orientations “live”. A positive correlation was found between participants' musical training and their acuity. The relationship between auditory expertise via musical training and the lack of a relationship with visual imagery, suggests that early use of a SSD draws primarily on the mechanisms of the sensory modality being used rather than the one being substituted. If vision is lost, audition represents the sensory channel of highest bandwidth of those remaining. The level of acuity found here, and the fact it was achieved with very little experience in sensory substitution by naïve users is promising. (shrink)

According to Reid, color sensations are not extended nor are they arranged in figured patterns. Reid further claimed that ‘there is no sensation appropriated to visible figure.’ Reid justified these controversial claims by appeal to Cheselden's report of the experiences of a young man affected by severe cataracts, and by appeal to cases of perception of visible figure without color. While holding fast to the principle that sensations are not extended, Dugald Stewart tried to show that ‘a variety of colour (...) sensations is a necessary means for the perception of visible figure.’ According to John Fearn, two motives appear to be central to Reid's views about color sensations and extension: his commitment to the Cartesian doctrine of the immateriality of the soul, and his attempt to evade ‘Hume's dilemma’ about the existence and immateriality of the soul. (shrink)

Two theses appear to be central to Reid’s view of the visual field. By sight, we do not originally perceive depth or linear distance from the eye. By sight, we originally perceive the position that points on the surface of objects have with regard to the centre of the eye. In different terms, by sight, we originally perceive the compass direction and degree of elevation of points on the surface of objects with reference to the centre of the eye. I (...) consider various problems about distance perception and perception of position with regard to the centre of the eye raised by Reid’s texts. These questions are relevant to Reid’s description of the geometry of visibles as the “intrinsic” geometry of the surface of the sphere. (shrink)

Molyneux’s question, whether the newly sighted might immediately recognize tactilely familiar shapes by sight alone, has produced an array of answers over three centuries of debate and discussion. I propose the first pluralist response: many different answers, both yes and no, are individually sufficient as an answer to the question as a whole. I argue that this is possible if we take the question to be cluster concept of sub-problems. This response opposes traditional answers that isolate specific perceptual features as (...) uniquely applicable to Molyneux’s question and grant viability to only one reply. Answering Molyneux’s question as a cluster concept may also serve as a methodology for resolving other philosophical problems. (shrink)

How does the mind attribute external causes to internal sensory experiences? Adam Smith addresses this question in his little known essay ‘Of the External Senses.’ I closely examine Smith's various formulations of this problem and then argue for an interpretation of his solution: that inborn perceptual mechanisms automatically generate external attributions of internal experiences. I conclude by speculating that these mechanisms are best understood to operate by simulating tactile environments.

The functions of the somatosensory system are multiple. We use tactile input to localize and experience the various qualities of touch, and proprioceptive information to determine the position of different parts of the body with respect to each other, which provides fundamental information for action. Further, tactile exploration of the characteristics of external objects can result in conscious perceptual experience and stimulus or object recognition. Neuroanatomical studies suggest parallel processing as well as serial processing within the cerebral somatosensory system that (...) reflect these separate functions, with one processing stream terminating in the posterior parietal cortex (PPC), and the other terminating in the insula. We suggest that, analogously to the organisation of the visual system, somatosensory processing for the guidance of action can be dissociated from the processing that leads to perception and memory. In addition, we find a second division between tactile information processing about external targets in service of object recognition and tactile information processing related to the body itself. We suggest the posterior parietal cortex subserves both perception and action, whereas the insula principally subserves perceptual recognition and learning. (shrink)

There have recently been various empirical attempts to answer Molyneux’s question, for example, the experiments undertaken by the Held group. These studies, though intricate, have encountered some objections, for instance, from Schwenkler, who proposes two ways of improving the experiments. One is “to re-run [the] experiment with the stimulus objects made to move, and/or the subjects moved or permitted to move with respect to them” (p. 94), which would promote three dimensional or otherwise viewpoint-invariant representations. The other is “to use (...) geometrically simpler shapes, such as the cube and sphere in Molyneux’s original proposal, or planar figures instead of three-dimensional solids” (p. 188). Connolly argues against the first modification but agrees with the second. In this article, I argue that the second modification is also problematic (though still surmountable), and that both Schwenkler and Connolly are too optimistic about the prospect of addressing Molyneux’s question empirically. (shrink)