Ragnar Arthur Granit was born in Helsinki, Finland, on October 30, 1900, the eldest son of Arthur W. Granit, a government forester, and Albertina Helena Malmberg Granit. Since both his parents were of Swedish origin, Granit attended the Swedish Normal School there. In 1918, Granit fought in Finland's war for independence from the Soviet Union, for which he received the Finnish Cross of Freedom.

The following year Granit entered the University of Helsinki with the intention of studying experimental psychology. However, he decided that a medical education would provide the best foundation for this field. So he went on to complete a master's degree in 1923 and then an M.D. in 1927. It was while completing his medical studies that Granit became interested in studying the nervous system, particularly the eye. The English physiologist Edgar Douglas Adrian had just made the first recordings of electrical impulses in single nerve fibers, and Granit...