This book takes a new and up-to-date look at the prominent theory that the left hemisphere is specialised for representing patterns extended in time whereas the right hemisphere represents simultaneous or 'spatial' patterns. What makes it unique in the field is that it looks at this theory from a neurobiological basis. It suggests that the difference resides in the range of conduction times in the axons connecting different regions of the cortex in each hemisphere. This hypothesis is discussed with respect to theoretical models of brain dynamics, and both gross and microscopic structure of the hemispheres. It deals with the psychological implications of the hypothesis for higher functions of the human cerebrum and outlines testable implications wherever possible.