Recognizing faces is the job of a select network of areas in the brain. Now researchers at The Rockefeller University working with rhesus macaque monkeys, whose face-processing systems closely resemble our own, have discovered two previously unknown areas of the brain involved in face recognition: areas capable of integrating visual perception with different kinds of memory. Humans process familiar and unfamiliar faces very differently. We may excel at recognizing pictures of familiar faces even when they are poorly lit or shot at awkward angles. But it’s difficult for us to recognize even slightly altered images of a face that is unfamiliar to us. Using functional magnetic resonance imaging, the researchers measured the animals’ brain activity as they responded to pictures of other monkeys’ faces. Those faces fell into three categories: personally familiar ones belonging to monkeys that the macaques had lived with for years; visually familiar ones whose pictures they had seen hundreds of times; and totally unfamiliar ones. The researchers expected the macaque face processing network to respond in much the same way to the first two types of faces. But no. The entire system showed more activity in response to the faces of long-time acquaintances. Faces that were merely familiar, actually caused a reduction of activity in some areas. Even more surprising was that the faces of animals whom the macaques had known for years prompted the activation of two previously unknown face-selective areas. One is located in a region of the brain associated with declarative memory, which consists of facts and events that can be consciously recalled. The other area is embedded in a region associated with social knowledge, such as information about individuals and their position within a social hierarchy.