Talk (Work in Progress): Alastair Isaac (Edinburgh)
Isomorphisms between Mind and World: The Challenge from Multidimensional Scaling
Phenomenal experience, the physical world, and neural activation stand in a three-way relationship of structural correspondence — one research program in psychology aims to cash this correspondence out in terms of isomorphisms. For example, the colors I can experience form a three-dimensional “color solid,” this solid is isomorphic to the space of neural activation defined by the wiring between cone cells in the retina and opponent cells in the LGN, and the physically defined space of possible surface reflectance profiles is homomorphic to both these spaces. Multidimensional scaling is a technique for compressing a large-dimensional data set into a low-dimensional space. It can be used, for instance, to extract a geometrical representation of possible experiences (say, of color) from psychophysical data. What happens to our nice, 3-way isomorphism-based, research program in perceptual psychology when the perceptual spaces derived from multidimensional scaling are not isomorphic to neural (or physical) structure? As it turns out, this is the actual situation — color experience, for instance, is at least 5 dimensional, a fact not easily reconcilable with our knowledge of the neural wiring of color vision.