SD–IE and other differentiation effects in Italy and Spain

Abstract SD–IE is a strategic differentiation effect present amongst indices of life history (LH), such that persons and populations of slow LH are more differentiated compared to those of fast LH. We found that this phenomenon is present amongst provinces in Italy and Spain, similarly to demonstrations among US states and Japanese prefectures. The average effect size of SD–IE was found to be bigger in Spain and Italy. We also tested cognitive differentiation as a function of life history speed and IQ (high- K and high-IQ provinces having higher cognitive differentiation), and found that these effects are also present in the Italian and Spanish regions. Most cognitive differentiation effects were statistically significant in spite of the small number of provinces, but all trended in the predicted direction. We discuss the findings from a bio-historical perspective, taking into account the ethnic variability present in Spain and Italy.