Here is a rendering of the corpus callosum with some of the grey matter stripped away in order to reveal how extensive its fibers are throughout the cerebral hemispheres. The corpus callosum is a large system of nerve fibers connecting the right and left hemispheres. We know something about its functioning through the split-brain operation, slicing it through to contain otherwise intractable seizures and from brain imaging studies. We know that it is larger in females than males, so that the research cited earlier on 12/10/12 showing greater inter-hemispheric connectivity for females and greater intra-hemispheric connectivity for males and which result in sexually stereotypical patterns of social strengths and particular task focus is consistent with neuroanatomical research. It is not mature at birth and so any mutual communication between right and left sides must be done through other, lower structures, mostly through bilateral processes. As it does mature, maybe from 2 1/2 and 4 1/2 years of age, left and right begin to inhibit the other in some functions, freeing the left to process language and other more abstract information and relegating to the right the necessary streaming of current information, e.g., the sensorium, body orientation, social interactions, etc.
Here is the maturational pinnacle. Around age 3 1/2 the hemispheres have separated in function and then, I think, they reconnect in a new way and the child realizes that these words used with people have an immediate meaning of something he or she has created in their own mind. It is a coupling of possibility to the here and now and it is, I believe, the first epiphany of mind.