The secular increase in test scores is a “Jensen effect”

The “Jensen effect” results from the correlation between the g factor and a huge number of psychological and biological variables. Although Rushton (Rushton, J. P. (1999). Secular gains in IQ not related to the g factor and inbreding depression — unlike Black–White differences: a reply to Flynn. Personality and Individual Differences, 26, 381–389) proposed that the secular increase in test scores is not a “Jensen effect”, the present study demonstrates that this is true for crystallized tests but not for fluid tests. A fluid g factor is correlated with the generational changes observed in two successive Spanish standardizations of the DAT battery. Contrary to Rushton’s (1999) findings — based on a crystallised g — there is a positive correlation between a fluid g and the generational cognitive change. There is one strong implication of the generational cognitive difference observed in the present study for the comparison of contemporary human populations: an environmental explanation of the current cognitive gap between some populations need only posit that the current average environment for population A (with a lower average score) matches the quality of the average environment for population B (with a higher average score) a generation ago.