b>. Computational models of colour vision assume that the biological function of colour vision is to detect surface reflectance. Some philosophers invoke these models as a basis for 'externalism' about perceptual content (content is distal) and 'objectivism' about colour (colour is surface reflectance). In an earlier article (Thompson et al. 1992), I criticized the 'computational objectivist' position on the basis of comparative colour vision: There are fundmental differences among the colour vision of animals and these (...) differences do not converge on the detection of any single type of environmental property. David R. Hilbert (1992) has recently defended computational objectivism against my 'comparative argument;' his arguments are based on the externalist approach to perceptual content originally developed by Mohan Matthen (1988) and on the computationally inspired theory of the evolutionary basis for trichromacy developed by Roger N. Shepard (1990). The present article provides a reply to Hilbert with extensive criticism of both Matthen's and Shepard's theories. I argue that the biological function of colour vision is not to detect surface reflectance, but to provide a set of perceptual categories that can apply to objects in a stable way in a variety of conditions. Comparative research indicates that both the perceptual categories and the distal stimuli will differ according to the animal and its visual ecology; therefore externalism and objectivism must be rejected. (shrink)

Studying colour vision across various species suggests that different species perceive different colours (the Disunity Hypothesis). It is plausible that all species’ color visual systems are, at least in principle, equally correct/veridical regarding colour (Ecumenicism). Assuming that colours are mind-independent features of material objects (Objectivism), it follows that objects simultaneously have different colours for different species (Pluralism). But are all these colours compatible with one another? Some have argued that they are on grounds that, while comparisons between colours (...) are possible within a given species’ colour space, they are not possible across the colour spaces of different species. Since colours from different spaces are not comparable, they cannot be incompatible. Hence, a given object can have a colour from as many colour spaces as needed to explain interspecies variations in colour perception. I argue that this reasoning is flawed in two ways. First, colour spaces that are non-comparable in pure or abstract reasoning, may nonetheless be comparable in applied contexts. Second, in our applied context – our world – evidence suggests that incompatibilities between colours from different species’ spaces are extremely likely when Colour Objectivism is presumed. But then the Pluralist solution to interspecies variation seems unavailable to the colour objectivist. (shrink)

It seems intuitively obvious that metameric matching of color samples entails a loss of information, for spectrophotometrically diverse materials appear the same. This intuition implicitly relies on a conception of the function of color vision and on a related conception of how color samples should be individuated. It assumes that the function of color vision is to distinguish among spectral energy distributions, and that color samples should be individuated by their physical properties. I (...) challenge these assumptions by articulating a different conception of the function of color vision, according to which color vision serves to partition object surfaces into discrimination classes. (shrink)

In specifying the sensory evidence for perceptual belief, thinkers have either chosen a common perceptual idiom or have invented one of their own as a starting-point for their enquiries. It is becoming clearer that the choice harbours crucial, often disputable, assumptions. I compare two sorts of constructions, a variety of propositional ones and an objectual one, and I argue that the objectual idiom is indispensable in order to explain how a perceptual belief can arise out of what is not already (...) a belief. This has implications not only for the question of how belief is generated from perceptual evidence, but also for various other controversies. I discuss two of these implications: the character of inferences from evidence, and basic belief. (shrink)

What is color? What is color vision? Most philosophers answer by reference to humans: to human color qualia, or to the environmental properties or "quality spaces" perceived by humans. It is argued, with reference to empirical findings concerning comparative color vision and the evolution of color vision, that all such attempts are mistaken. An adequate definition of color vision must eschew reference to its outputs in the human cognition and (...) refer only to inputs: color vision consists in the use of wavelength discrimination in the construction of visual representations. A color quality is one that is generated from such processing. (shrink)

A stubborn problem for reflectance physicalism about color is to account for individual differences in normal trichromat color perception. The identification of determinate colors with physical properties of visible surfaces in a universal, perceiver-independent way is challenged by the observation that the same surfaces in identical viewing conditions often look different in color to different human subjects with normal color vision. Recently, leading representatives of reflectance physicalism have offered some arguments to defend their view against (...) the individual differences challenge. In this paper I challenge their defense. I argue thateven though individual differences are present in shape perception as well as in color perception, the mechanisms of shape perception and those of color perception differ in ways which make them completely different regarding their evidential status for certain identity claims. Thus comparing color perception to shape perception offers no support for identifying hues with reflectances. On the other hand, drawing a parallel between the temperature-mean kinetic energy of molecules (MKE) identification and the proposed hue-reflectance identities is no support for reflectance physicalism either, since there is an important disanalogybetween the two cases. While individual differences obtain in color perception, the effects of temperature (e.g., melting, thermal expansion) do not exhibit analogous variation, which makes the temperature-MKE identification unproblematic compared to the hue-reflectance identification. One motivation for this ongoing debate is that the success or failure of reflectance physicalism has far-reaching consequences regarding externalist theories of phenomenal consciousness. (shrink)

It seems almost a truism to say that colour is a sensation; and yet Young, by honestly recognizing this elementary truth, established the first consistent theory of colour. So far as I know, Thomas Young was the first who, starting from the well-known fact that there are three primary colours, sought for the explanation of this fact, not in the nature of light, but in the constitution of man. (James Clerk Maxwell, p. 267.)It is doubtless scientific to disregard certain aspects (...) when we work; but to urge that therefore such aspects are not fact, and that what we use without them is an independent real thing-this is barbarous metaphysics. (F. H. Bradley, p. 15.). (shrink)

This volume is the first collection of articles dedicated to Wittgenstein s thoughts on colour, focusing in particular on his so-called Remarks on Colour, a piece of writing that has received comparably little attention from Wittgenstein scholars. The articles discuss why Wittgenstein wrote so intensively about colour during the last years of his life andwhat significance these remarks have for understanding his philosophical work in general.".

A stubborn problem for reflectance physicalism about color is to account for individual differences in normal trichromat color perception. The identification of determinate colors with physical properties of visible surfaces in a universal, perceiver-independent way is challenged by the observation that the same surfaces in identical viewing conditions often look different in color to different human subjects with normal color vision. Recently, leading representatives of reflectance physicalism have offered some arguments to defend their view against (...) the individual differences challenge. In this paper I challenge their defense. I argue thateven though individual differences are present in shape perception as well as in color perception, the mechanisms of shape perception and those of color perception differ in ways which make them completely different regarding their evidential status for certain identity claims. Thus comparing color perception to shape perception offers no support for identifying hues with reflectances. On the other hand, drawing a parallel between the temperature-mean kinetic energy of molecules (MKE) identification and the proposed hue-reflectance identities is no support for reflectance physicalism either, since there is an important disanalogybetween the two cases. While individual differences obtain in color perception, the effects of temperature (e.g., melting, thermal expansion) do not exhibit analogous variation, which makes the temperature-MKE identification unproblematic compared to the hue-reflectance identification. One motivation for this ongoing debate is that the success or failure of reflectance physicalism has far-reaching consequences regarding externalist theories of phenomenal consciousness. (shrink)

What is the most important reason for using Computer Vision methods in humanities research? In this article, I argue that the use of numerical representation and data analysis methods offers a new language for describing cultural artifacts, experiences and dynamics. The human languages such as English or Russian that developed rather recently in human evolution are not good at capturing analog properties of human sensorial and cultural experiences. These limitations become particularly worrying if we want to compare thousands, millions (...) or billions of artifacts—i.e. to study contemporary media and cultures at their new twenty-first century scale. When we instead use numerical measurements of image properties standard in Computer Vision, we can better capture details of a single artifact as well as visual differences between a number of artifacts–even if they are very small. The examples of visual dimensions that numbers can capture better then languages include color, shape, texture, contours, composition, and visual characteristics of represented faces, bodies and objects. The methods of finding structures and relationships in large numerical datasets developed in statistics and machine learning allow us to extend this analysis to very big datasets of cultural objects. Equally importantly, numerical image features used in Computer Vision also give us a new language to represent gradual and continuous temporal changes—something which natural languages are also bad at. This applies to both single artworks such as a film or a dance piece and also to changes in visual characteristics in millions of artifacts over decades or centuries. (shrink)

Colour vision plays a foundational explanatory role in the philosophy of colour, and serves as perennial quarry in the wider philosophy of perception. I present two contributions to our understanding of this notion. The first is to develop a constitutive approach to characterizing colour vision. This approach seeks to comprehend the nature of colour vision qua psychological kind, as contrasted with traditional experiential approaches, which prioritize descriptions of our ordinary visual experience of colour. The second contribution is (...) to argue that colour vision does not constitutively involve the ability to see colours, in a natural and categorically committed sense. I argue that two subjects exactly alike in respect of their constitutive colour vision abilities could differ in respect of whether or not they have categorical perception of colour. The argument is supported by thought experiment and dissociations observed in cognitive neuropsychology. The argument also bears connections to recent neo-Whorfian accounts of colour categorization. _1._ Introduction _2._ Colour Vision, Experience, and Natures _3._ The Central Argument _3.1._ Colour constancy and discrimination _3.2._ Dissociating colour vision and categorical perception for colour _4._ Whorf and the View from Cognitive Neuropsychology _5._ Conclusion. (shrink)

The thresholds of human observers detecting line targets improve significantly when the targets are presented in a spatial context of collinear inducing stimuli. This phenomenon is referred to as spatial facilitation, and may reflect the output of long-range interactions between cortical feature detectors. Spatial facilitation has thus far been observed with luminance-defined, achromatic stimuli on achromatic backgrounds. This study compares spatial facilitation with line targets and collinear, edge-like inducers defined by luminance contrast to spatial facilitation with targets and inducers defined (...) by color contrast. The results of a first experiment show that achromatic inducers facilitate the detection of achromatic targets on gray and colored backgrounds, but tend to suppress the detection of chromatic targets. Chromatic inducers facilitate the detection of chromatic targets on gray and colored backgrounds, but tend to suppress the detection of achromatic targets. Chromatic spatial facilitation appears to be strongest when inducers and background are isoluminant. The results of a second experiment show that spatial facilitation with chromatic targets and inducers requires a longer exposure duration of the inducers than spatial facilitation with achromatic targets and inducers, which is already fully effective at an inducer exposure of 30 ms only. The findings point towards two separate mechanisms for spatial facilitation with collinear form stimuli: one that operates in the domain of luminance, and one that operates in the domain of color contrast. These results are consistent with neural models of boundary and surface formation which suggest that achromatic and chromatic visual cues are represented on different cortical surface representations that are capable of selectively attracting attention. Multiple copies of these achromatic and chromatic surface representations exist corresponding to different ranges of perceived depth from an observer, and each can attract attention to itself. Color and contrast differences between inducing and test stimuli, and transient responses to inducing stimuli, can cause attention to shift across these surface representations in ways that sometimes enhance and sometimes interfere with target detection. (shrink)

Different explanations of color vision favor different philosophical positions: Computational vision is more compatible with objectivism (the color is in the object), psychophysics and neurophysiology with subjectivism (the color is in the head). Comparative research suggests that an explanation of color must be both experientialist (unlike objectivism) and ecological (unlike subjectivism). Computational vision's emphasis on optimally prespecified features of the environment (i.e., distal properties, independent of the sensory-motor capacities of the animal) is (...) unsatisfactory. Conceiving of visual perception instead as the visual guidance of activity in an environment that is determined largely by that very activity suggests new directions for research. (shrink)

Colour fascinates all of us, and scientists and philosophers have sought to understand the true nature of colour vision for many years. In recent times, investigations into colour vision have been one of the main success stories of cognitive science, for each discipline within the field - neuroscience, psychology, linguistics, computer science and artificial intelligence, and philosophy - has contributed significantly to our understanding of colour. Evan Thompson's book is a major contribution to this interdisciplinary project. Colour (...) class='Hi'>Vision provides an accessible review of the current scientific and philosophical discussions of colour vision. Thompson steers a course between the subjective and objective positions on colour, arguing for a relational account. This account develops a novel `ecological' approach to colour vision in cognitive science and the philosophy of perception. It is vital reading for all cognitive scientists and philosophers whose interests touch upon this central area. (shrink)

This book is a major contribution to the interdisciplinary project of investigating the true nature of color vision.

What is colour vision for? In the popular imagination colour vision is for “seeing the colours” — adding hue to the achromatic world of shape, depth and motion. On this view colour vision plays little more than an ornamental role, lending glamour to an otherwise monochrome world. This idea has guided much theorising about colour within vision science and philosophy. However, we argue that a broader approach is needed. Recent research in the psychology of colour demonstrates (...) that colour vision is integral to a variety of visual processes, helping us to perform many types of visual tasks. We discuss some of this research and consider its implications for philosophical theories of colour. (shrink)

The primary issues concern whether objects have colours, and what sorts of properties the colours are. Some philosophers hold that nothing is coloured, others that colour are powers to affect perceivers, and others that colours are physical properties.

There are serious reasons for accepting each of these propositions individually but there are apparently insurmountable difficulties with accepting all three of them simultaneously if we assume that color is a single property. 1) and 2) together seem to imply that there is some property which all organisms with color vision can see and 3) seems to imply that there can be no such property. If these implications really are valid then one or more of these propositions (...) will have to be rejected in spite of whatever reasons can be given for their apparent acceptability. Before going on to discuss possible resolutions of this apparent contradiction it is worth pointing out there our three propositions are not all of a kind. Proposition 1) is a metaphysical thesis about the ontological status of color and proposition 3) is an empirical thesis about what properties organisms with color vision are capable of detecting. If you accept 1) then 2) will appear to verge on the trivial, but if 1) is denied then the status of 2) will appear more problematic. In what follows I will have more to say about why we either should or should not accept all three of these propositions. (shrink)

Amblyopia, or lazy eye, is a neurological vision disorder that studies have shown to affect two to five percent of the population. Current methods of treatment produce the best visual outcome, if the condition is identified early in the patient's life. Several early screening procedures are aimed at finding the condition while the patient is a child, including an automated vision screening system. This paper aims to use artificial intelligence techniques to automatically identify children who are at risk (...) for developing the amblyopic condition and should therefore be referred to a specialist, i.e., pediatric ophthalmologist. Three techniques, namely, decision tree learning, random forest, and artificial neural network, are studied in this paper in terms of their effectiveness, using metrics of sensitivity, specificity, and accuracy. The features used by the techniques are extracted from images of patient eyes and are based on the color information. The efficacy of pixel color data is investigated with respect to the measurement of the rate of change of the color in the iris and pupil, i.e., color slope features. A 10-fold stratified cross validation procedure is used to compare the effectiveness of the three AI techniques in this medical application domain. (shrink)

The standard adaptationist explanation of the presence of a sensory mechanism in an organism--that it detects properties useful to the organism--cannot be given for color vision. This is because colors do not exist. After arguing for this latter claim, I consider, but reject, nonadaptationist explanations. I conclude by proposing an explanation of how color vision could have adaptive value even though it does not detect properties in the environment.

The standard adaptationist explanation of the presence of a sensory mechanism in an organism—that it detects properties useful to the organism—cannot be given for color vision. This is because colors do not exist. After arguing for this latter claim, I consider, but reject, nonadaptationist explanations. I conclude by proposing an explanation of how color vision could have adaptive value even though it does not detect properties in the environment.

Tracking theories of mental representation posit a privileged relation between color representations and the color properties of objects. Tracking theories of mental representation have been used to motivate color realism as they posit that the function of color vision is to represent the colors of objects. It has been argued that tracking theories have a major flaw, namely they cannot account for reliable misrepresentation. It has further been suggested that reliable color misrepresentation is a (...) live possibility. In this chapter, I argue that the current evidence indicates that our color representations reliably misrepresent. This conclusion undermines tracking theories and the color realist theories they purport to motivate. (shrink)

A survey of color science and color vision.

The topic of colour vision is one that integrates research from psychology, neuroscience, biology, ophthalmology, physics, and genetics. How do we make sense of colour in the world, and how has such an ability evolved in humans? How does the brain interpret colour images? Do men discriminate colours differently from women? Why do some people have problems perceiving colours? Mollon, Pokorny, and Knoblauch are leading authorities on this topic, and together they have brought together a stellar list of contributors, (...) encompassing all these fields. (shrink)

The qualitative and quantitative properties of color sensations and neuronal color coding are discussed in relation to physiological color exchanges and their evolutionary constraints. Based on the identity mind/matter thesis, additional physical measurements on color sensations are described that will allow us, at least in principle, to compare the qualitative properties of color sensations in different brains.

A critical survey of recent work on the ontological status of colors supports the conclusion that, while some accounts of color can plausibly be dismissed, no single account can yet be endorsed. Among the remaining options are certain forms of color realism according which familiar colors are instantiated by objects in our extra-cranial visual environment. Also still an option is color anti-realism, the view that familiar colors are, at best, biologically adaptive fictions, instantiated nowhere.I argue that there (...) is simply no fact of the matter as to which of these remaining options is correct. I blame this indeterminacy on the fact that color vision exhibits several of the hallmarks of a modular input system, as described by Jerry Fodor in The Modularity of Mind. (shrink)