Hering enrolled at the University of Leipzig at the age of 19. He was a student of such famous men as E. H. Weber and Gustav Fechner, and was also much impressed with the work of Johannes Muller. Later he became professor of physiology at Leipzig and then at the Academy at Vienna. During the 1860s Hering devoted himself to the study of visual space perception. With regard to visual perception he fostered the doctrine of nativism, the view that one can judge space and depth in an inherent way. This idea was later taken up by the Gestalt psychologists, but in Hering's time it was in opposition to the more empirical approach of Hermann Helmholtz. In the 1870s Hering devoted himself to the development of a theory of color vision in opposition to that of Helmholtz. According to Hering's theory, the retina of the eye had different substances for responding to red-green, blue-yellow and black-white, each of which could be excited by either of the opposing reactions. There could be a dissimilation (catabolism) or an assimilation (anabolism). The dissimilative reaction responded to red, yellow, and white, while the assimilative one responded to the opposite dimensions of green, blue, or black. The theory also explained negative afterimages and color contrast which gave opposite reactions to the initial stimulation. For example, if one focuses on yellow, the negative afterimage will be blue, and so forth. Each color was believed to produce a chemical change in the various receptors in the eye. The afterimage was stimulated by the opposite reaction of the initial color presented. The theory also explained color blindness. Redand green color blindnesstend to go together. For about 50 years Herings theory was widely held to that of Helmholtz.