From a psychological perspective, studies are showing that cognitive capacity “most often determines whether people can attain extreme old age while remaining active” (Volz, 2000). The good news is that research by psychologists at Princeton University demonstrated that new brain cells, which enable learning and memory, grow continuously throughout a person’s lifetime."It is cognitive capacity, more than any physical disability," says Margery Silver, EdD, a neuropsychologist at Harvard,"that most often determines whether people can attain extreme old age while remaining active." .