The present study was intended to provide perspective, albeit less than unequivocal, on the research of Lynn (2010) who reported higher IQs in the northern than southern Italian regions. He attributes this to northern Italians having a greater genetic similarity to middle Europeans and southern Italians to Mediterranean people. Higher regional IQ was associated with biological variables more characteristic of middle European than Mediterranean populations (cephalic index, eye color, hair color, multiple sclerosis rates, schizophrenia rates). It was maintained, however, that very confident and definitive inferences regarding genetic regional differences in IQ are not warranted. Social conceptualized variables also correlated significantly with IQ so as to suggest the importance of nutrition and economic developmental status more generally.
One should also bear in mind that the correlations are ecological correlations and have the limitations associated with such. Prince (1998) succinctly described three problems with ecological correlations. One problem, the "ecological fallacy," is that people who are high or low in one variable are not necessarily the same people who are high or low on the other variable. In the present study the people in a region who are high in cephalic index are not necessarily the same people who are high in IQ. The second problem is that a third variable may be responsible for the correlation between the other two. In the present study, temperature, precipitation, constituents of drinking water, constituents of soil, health, genetic predisposition to medical disorder, nutrition, and medical care are some of the variables that could conceivably influence the correlation of IQ with schizophrenia and multiple sclerosis. The third problem is that cause and effect cannot be determined.
It is apparent that regions that have at least some biological characteristics more common in middle European than Mediterranean populations (higher cephalic index, lighter eye color and hair, and higher rates of multiple sclerosis and schizophrenia) tend to have higher IQs. This could be viewed consistent with Lynn's (2010) assertion of a genetically based explanation of north-south IQ differences. Great caution, however, is urged regarding such inferences. Since these are ecological correlations, the persons high or low in these biological variables may not be the same persons in that region high or low in IQ. Because some characteristics are different does not mean that all characteristics are different. East Asians have different facial features than Europeans and Africans. These differences, however, may be only remotely related or not related at all to IQ differences. Also, there are notable exceptions to generalizations about IQ and coloration. Most East Asians and Jewish persons are darker than Scandinavians and yet have higher mean IQs. Furthermore, social variables could account, at least in part, for the north-south IQ differences. Nevertheless, examination and discussion of the biological variable findings are warranted.
The social correlations with IQ and latitude were also substantial and could be viewed as indicating social explanations of the north-south IQ differences. As reasoned above, the massive illiteracy of the south (and even in the north to a lesser extent) could not be explained mainly by genetically determined intelligence. The positive correlation between IQ and literacy suggests that the lower developmental stature of the southern region contributes to the lower IQ. Such an interpretation is also suggested by, as hypothesized, the negative correlation between IQ and percentage increase in stature and negative correlation between income and latitude. This correlation also shows that those regions with the greatest history of malnutrition have lower IQs. As pointed out by Lynn (1990), the secular increase in IQ and stature parallel each other and both seem to be a function of improved nutrition.
Donald I. Templer. "Biological correlates of northern-southern Italy differences in IQ". Intelligence, 2012.