The Comparative Method in Cross-Cultural and Cross-Species Research

Abstract

Comparative methodology is controversial in biology and the related field of research on behavioral and psychological traits across human cultures. We critically examine this controversy. We argue that the widely held opinion of non-independence among historically-related cultures and species errs by not recognizing and incorporating into research the two distinct and complementary categories of causation that account for an extant trait-the phylogenetic origin of the trait (cultural or otherwise) and the maintenance of the trait after its phylogenetic origin. Phylogenetic correction for non-independence is required in the comparative study of a trait's phylogenetic origin, but is irrelevant for the comparative study of the causation of a trait's maintenance after its phylogenetic origin. Across cultures, even closely related cultures, causes that are specific to each culture act to maintain cultural similarities, which makes such similarities independent. Among species, even closely related species, similarities are maintained by lineage-specific, and hence independent, evolutionary causal processes. Comparative methodology has been criticized as being inferior to other types of scientific methodology (e.g., experimentation), because it is based on correlational data. This criticism is erroneous because, all scientific findings are correlational, and in hypothesis testing, the ability of an empirical finding to address causation depends solely upon the control of confounding variables, not the type of scientific method itself. © 2013 Springer Science+Business Media New York.