Sensory integration and the unity of consciousness
Based on but not limited to material from a conference at Brown University in 2011, Sensory Integration and the Unity of Consciousness is an ambitious collection that brings together two distinct but intertwined topics.1 In what follows, I briefly explain what sensory integration and the unity of consciousness amount to, highlight the contents of the papers, and finally end with general observations and suggestions. I will spend more time on sensory integration, since it is relatively unfamiliar terrain in philosophy. "Sensory integration" can refer to several phenomena that have been studied by psychology and cognitive neuroscience. First, it can mean cue combination, the phenomenon whereby perceivers can detect single properties by combining information from a variety of information channels. The perceptual system takes a weighted average of estimates from these sources, with weights proportional to the reliability of the sources in question. Second, it can mean cross modal interactions, one paradigm example being the McGurk Effect: dubbing the phoneme /ba/ onto the lip movements for ga/ produces a percept of the phoneme /da/ (McGurk MacDonald, 1976) The sound induced flash illusion is another prominent case (Shams, Kamitani, Shimojo, 2000) There are also versions of binding problems: how do we detect multiple properties through disparate neural processes in a way that results in experiences of those properties as bound to the very same object? Temporal factors makes things more complicated: varieties of sensory information travel from separate channels with different distances and speeds, but the resulting percepts do not seem to be temporally disjoint in most cases. Common sensibles are a third kind of sensory integration. For example, both sight and touch detect spatial properties, but there is a question concerning whether there are amodal representations underlying both of them. This is not the place to elaborate on these different kinds of sensory integrations; the papers in this volume provide very detailed discussions of them. I shall now turn to the unity of consciousness.2 Like sensory integration, there are different kinds of unities of consciousness, the most discussed ones being phenomenal unity (Bayne Chalmers, 2003) and representational unity (Tye, 2003) Very often, we have multiple experiences from different sense modalities simultaneously, such as tactile experiences of touching keyboards and auditory experiences of listening to music at the same time. Many argue that these experiences are phenomenally unified. Exactly how we can characterize this idea is itself a challenging issue. According to many philosophers, experiences have representational contents, so a parallel notion of representational unity in terms of content can be formulated. There is a further question as to whether one is explanatorily prior to the other. Following the representationalist tradition, some have argued that representational unity can be invoked to explain phenomenal unity Pizlo, Z. (2010) 3D shape: Its unique place in visual perception. Cambridge: MIT Press. Sober, E. (1976) Mental representations. Synthese, 33(1) 101 148. Walton, K. (1984) Transparent pictures. Critical Inquiry, 11(2) 246 277. Wollheim, R. (1974) On art and the mind. Cambridge, MA: Harvard University Press.