Increases in black IQ: In an earlier post, I showed that white Baby Boomers are smarter than earlier and later cohorts. What about blacks? Here are Wordsum means:
Mean Wordsum scores--blacks
1920-39 birth cohort 4.31
1940-59 birth cohort 5.22
1960-79 birth cohort 5.37
Blacks born in the forties and fifities are significantly smarter than the older cohort. Those born in the sixties and seventies have an even higher average, but the increase is not statistically significant.
How do we account for this? Offering an explanation for the post-Baby Boom IQ decrease among whites, Agnostic wrote that there was a dietary shift away from fat and protein and toward carbohydrates in the 1970s. "Fat and cholesterol are crucial for learning and memory, so when people start relying more on potatoes, pasta, bread, and fruit juice, compared to bacon, eggs, cheese, and milk, we'd expect them to have somewhat lower vocabulary scores."
Could it be that black Baby Boomers enjoyed the richer diet that whites had in 40s and 50s, and that in more recent decades they have been slower to switch to high-carb diets? My impression is that lower-class folks to this day worry less about their fat and cholesterol intake (although they are fatter).
Historical gains in IQ have been observed mostly among the left-half of the bell curve, and Americans at the highest vocabulary levels have been dwindling. The post-war prosperity improved the diet of those with modest incomes more than the wealthy, and in more recent decades higher-income people have avoided fatty foods more than everyone else. The facts seem to support Agnostic.