PubMed1979
According to Darwin's theory of evolution by natural selection, the existence of mental operations proves their usefulness. Darwin called himself a mental materialist. This is one scientific theory of consciousness. Human consciousness has three useful aspects: awareness, intentionality and sharing with others. All have simple equivalents in animals. The latter two are neglected in neurophysiology and experimental psychology. Developmental, neuroanatomical and neuropsychological evidence shows that the human brain has innate structures of awareness, intentionality and interpersonal sharing. Human life depends on interpersonal cooperation. We may have a conscious self, but consciousness of others is essential in us. Studies of commissurotomy patients demonstrate the elaborate interconnected neural organization of consciousness and provide evidence of underlying and necessary levels of motivation, perception and motor integration below consciousness. Additionally, they show that awareness may be split into two different modes. These regulate one another during development and are complementary in culturally sophisticated adult life. One hemisphere, usually the left, has responsibility for expressing ideas and purposes in language. The other responds to the phenomenal context and the subjective situation. Both have human experiences and purposes. Both still collaborate in a unified intentional system after commissurotomy. Infant studies reveal that language develops out of an interpersonal mental process. This seems to control development of thinking. Thus notions of the newborn as an isolated amoral id, and of the infant as an egocentric discoverer of the object concept, must be rejected. Cultivation of moral awareness and a sense of purpose guided by meanings and values depends on innate organization of the human brain for interpersonal consciousness.