Strategic differentiation and integration among the 50 states of the USA

Recent studies demonstrate that individuals and populations (at the scale of nations) exhibiting slower life history (LH) speeds are more differentiated amongst themselves with respect to the components of life history. Faster life history individuals and populations are more integrated by comparison. This phenomenon, termed strategic differentiation–integration effort (SD–IE), has not yet been tested on a national scale, however, which is an important remaining step in establishing its generalizability at different levels of aggregation among humans. SD–IE was tested with data on five LH variables from the fifty states of the US. Effects supportive of the SD–IE hypothesis were found in all LH variables, with an average effect magnitude slightly larger than that found in studies of SD–IE at the individual differences level. This is putatively attributed to population stratification, due to the varied racial make-up of the population in the US, including European, African, Native American, and Asian ancestries from multiple countries. This study indicates that SD–IE is a generalizable phenomenon occurring at various levels of aggregation.