Differential k theory is a theory, first proposed by Canadian psychologist J. Philippe Rushton in 1985, which attempts to apply r/K selection theory to human races. According to Rushton, this theory explains race differences in fertility, IQ, criminality, and sexual anatomy and behavior. The theory also hypothesizes that a single factor, the "k factor", affects multiple population statistics Rushton referred to as "life-history traits".
Reaction
The theory has been criticized by some researchers. Its critics have argued that Rushton's predictions based on the theory "are supported by selective citation and misrepresentation of the research literature and by the use of unreliable sources" and that Rushton's methodology "indicates a lack of familiarity with ecological thinking and scientific method in general." In contrast, Donald Templer has reported evidence in support of the theory's prediction of a "k factor" that accounts for numerous life-history traits, such as "birth rate, infant mortality, HIV/AIDS, general intelligence, and life expectancy." A 2013 study found some support for the theory in regards to the correlation between IQ and two such traits: parental investment and fertility rates.