Psychologists and neuroscientists began to build bridges and linked their inquiries together. Both philosophers and scientists employ the term reduction in characterizing relations between the results of higher-level and basic-level inquiries that are supposedly jeopardized by multiple realization. This chapter describes an understanding of reduction provided by the framework of mechanistic explanation that fits with the pursuit's scientists label reductionistic. There are differences between the mechanisms in different species that result in what are treated as the same phenomena. The chapter takes up this issue directly and discusses that the same standards of typing are applied to phenomena as to realizations. It considers what happens when one uses a coarser grain to type neural phenomena. The chapter presents the research on circadian rhythms as an exemplar as this is a field in which the issues concerning multiple realization, conservation of mechanism, and identity.