ABSTRACT
The multilevel taxonomic classification scheme of perceptually significant processes that I propose in this book is aimed at describing and classifying the significant neural and psychologicaP transforms imposed upon the stream of
information defined by the proximal stimulus scene. However the first, and not necessarily the least powerful, influence on visual perception occurs prior to the sensory transduction that converts the physical energies of the external environment to the electrochemical energies of the nervous system. This chapter considers those preneural stimulus transformations that occur either in the external environment or within the optical components of the eye that have been shown to be of measurable perceptual significance. I refer to these transformations as Level 0 processes to emphasize that although these transformations are perceptually influential, and in many cases may even be the result of biological mechanisms within the eye, they are mediated by predominantly linear physical processes, not by the more complex psychoneural ones.
