Homology in psychology, as in biology, refers to a relationship between characteristics that reflects the characteristics' origins in either evolution or development. Homologous behaviors can theoretically be of at least two different varieties.^[1] As with homologous anatomical characteristics, behaviors present in different species can be considered homologous if they are likely present in those species because the behaviors were present in a common ancestor of the two species. Alternatively, in much the same way as reproductive structures (e.g., the penis and the clitoris) are considered homologous because they share a common origin in embryonic tissues,^[2] behaviors—or the neural substrates associated with those behaviors^[3]—can also be considered homologous if they share common origins in development.

Behavioral homologies have been considered since at least 1958, when Konrad Lorenz studied the evolution of behavior.^[4] More recently, the question of behavioral homologies has been addressed by philosophers of science such as Marc Ereshefsky,^[5][6] psychologists such as Drew Rendall,^[7] and neuroscientists such as Georg Striedter and Glenn Northcutt.^[8] It is debatable whether the concept of homology is useful in developmental psychology.^[9][10][11]

For example, D. W. Rajecki and Randall C. Flanery, using data on humans and on nonhuman primates, argue that patterns of behaviour in dominance hierarchies are homologous across the primates.^[12]