Phenomenal Qualities and the Development of Perceptual Integration

Abstract

In this chapter, data concerning the development of principal aspects of vision is reviewed. First, the development of colour vision and luminance perception is discussed. Relevant data accumulated so far indicates that perception of colour and luminance is present by 6-9 months of age. The presence of typical color illusions at this age suggests that the phenomenal character of color experience is comparable to that of adults well before the first birthday. Thus it seems plausible that color perception develops on the grounds of genetically preprogrammed maturation, in which perceptual learning and plasticity play a limited role. This claim also seems to be supported by case studies of newly sighted patients. On the other hand, perceptual integration of edges and forms in the visual environment as well as the development of binocular vision, and the perception of ambiguous figures seem to depend crucially on early perceptual learning. Both developmental and clinical data indicate a more significant involvement of perceptual learning in such mid-level and higher level perceptual phenomena. Introduction When investigating perceptual development, an inherently interesting question is, what is children’s perceived world like, and how does it differ from that of adults? The data reviewed in this chapter is intended to shed some light on this question. Part of the question is, what can we know about children’s phenomenal experiences; is their experience, in terms of its phenomenal character, similar to that of adults? Perceptual experiences have a characteristically subjective aspect, which is accessible only from the subject’s first-person point of view, namely what it is like to undergo a given experience. This subjective aspect is called phenomenal character. In a sense, experiences are states of the brain, and they can be described as such – for example, in terms of neuroscience. But since your brain states (neuronal activities) do not, and cannot, occur in my brain, I cannot undergo your experiences. This is part of the explanation of what makes experience subjective. 1 In a broad sense, the terms ’qualia’ and ’phenomenal character’ have the same meaning: they refer to the subjective aspect of experiences (see the main text). The term ’qualia’, however, is more strongly associated with a certain theoretical conception of the nature of this subjective character, namely the idea that qualia are intrinsic properties of certain brain states. Intrinsic properties are local properties that follow from the way something is – mass and chemical composition are examples. Other (non-intrinsic) properties like weight or inflammability arise from how entities interact with the world. According to representational theories of phenomenal consciousness (e.g., Tye, 2000), the subjective aspect is not an intrinsic property of brain states, but rather it arises from how our brain states interact with the environment. Thus whether the subjective aspect of experiences is one of their intrinsic properties is a matter of debate. The term ’phenomenal character’ is a theoretically more neutral one for the subjective aspect than ’qualia’. 2 I can only study your brain activity, say, by brain imaging. But via the brain imaging equipment, I am not properly related to your brain activity to have the phenomenal experience that you have when that activity occurs in your brain. In this sense experiences are relational properties; an experience is, at a minimum, (i) a local neural activity which is (ii) properly related to the rest of one’s brain. These are two general conditions for