Strategic differentiation–integration effort amongst the 47 prefectures of Japan

The strategic differentiation–integration effort (SD–IE) hypothesis holds that high-K (slow life history) individuals and populations are specialists with respect to domains of behavior and personality, and that the converse is true for low-K populations. Here, we examine SD–IE at the national level, amongst the 47 prefectures of Japan. Aggregate data on height, IQ, divorce, homicide rates, skin reflectance, fertility rates, income and infant mortality were used as life history indicators. Principal Axis Factor analysis revealed the presence of a K super-factor on which the first five of these loaded preferentially. A second factor loaded highly on income and fertility and a third on infant mortality. As Japan is among the highest-K countries, the extraction of three factors indicates strong underlying SD–IE. Amongst the five K super-factor variables, SD–IE confirmatory effects were recovered on all variables except IQ. The effect magnitudes were positively mediated by the K super-factor saturation of the indicators. We conclude that SD–IE appears to be highly general across different populations and measures of life-history traits. Finally, we discuss how the second and third factors appear to conform to recent social phenomena specific to the Japanese culture, namely increasing behavioral asexuality and high-quality universal health coverage.