Because centenarians tend to have family members who are also long-lived, scientists have examined their DNA in hopes of identifying genes that may contribute to their longevity. These linkage analysis studies may lead to the development of life-extending medications. Large-scale studies of centenarians also point to the importance of factors in the psychological and social domains of health. Ray thrives on his curiosity as a scientist, while Elva enjoys painting and weekly outings with her friends.