A filmmaker who illuminates life in Mexico while reconceiving how documentaries are made. A flutist who built an organization that presents daring new music around the globe. A pediatric neurosurgeon who has saved the lives of uncounted children around the world by inventing an inexpensive, accessible way of treating hydrocephalus, or "water on the brain."

These are among the winners of 2012 MacArthur Fellowships, or "genius grants," which carry a great deal of prestige -- plus $500,000 dispensed in installments over five years. With no strings attached. A certain degree of mystery hovers over the MacArthurs, since no one can apply for them. Instead, potential candidates are evaluated without knowing it, the process delivering a new class of recipients each year since 1981. The Chicago-based John D. and Catherine T. MacArthur Foundation this year awards 23 individuals in the arts, sciences and humanities. Following is an annotated guide to this year's winners: -- Howard Reich