This study examines the whether there is a phylogenetic structure to such episodes of changes in encephalization across mammals. Researchers used phylogenetic techniques to analyze brain mass, body mass and encephalization quotient (EQ) among 630 extant mammalian species. All data on body mass and brain mass of mammals were collected from published literature sources, except for brain masses measured directly from post-mortem specimens the researchers' own collections, and have been entered into a MySQL database.