Comparative psychology is the scientific study of the behavior and mental processes of non-human animals, especially as these relate to the phylogenetic history, adaptive significance, and development of behavior. The phrase comparative psychology may be employed in a narrow and a broad meaning. In its narrow meaning, it refers to the study of the similarities and differences in the psychology and behavior of different species. In a broader meaning, comparative psychology includes comparisons between different biological and socio-cultural groups, such as species, sexes, developmental stages, ages, and ethnicities. Research in this area addresses many different issues, uses many different methods and explores the behavior of many different species from insects to primates.