In a small, windowless room at Johns Hopkins University, pigtail macaques jump around in cages. The braver ones reach out between the metal bars to accept pieces of apricot with their long fingers.
In one cage, a monkey hangs back in the corner. At first it looks like he's all alone in there, until veterinarian Bob Adams points out, "No, he's got a friend." Another monkey is clinging to his back, almost hidden.