Iodization of Salt in 1924 Increased American IQs 15 Points

Iodine deficiency is the leading cause of preventable mental retardation in the world today. The condition, which was common in the developed world until the introduction of iodized salt in the 1920s, is connected to low iodine levels in the soil and water. We examine the impact of salt iodization on cognitive outcomes in the US by taking advantage of this natural geographic variation. Salt was iodized over a very short period of time beginning in 1924. We use military data collected during W...

 Theories on Handedness

Because it develops so early, this brain asymmetry appears to be largely innate. It is possible, however, that environmental factors begin operating even before birth. One hypothesis is that the right hand becomes more skillfull because it has greater freedom to move in the womb. About three-quarters of all fetuses spend the last several weeks of gestation with their right arm facing out—toward the mother's abdominal wall. This arm has more space in which to move than does the left arm, whi...

 Fetal Alcohol Syndrom

It is from a public health standpoint, rather than from knowledge of indipercent of pregnant wompr. i^ percent of pregnant women in the United States reported drinking alcohol in the month preceding the survey, and 3 percent admitted to at least one binge. (Alcohol consumption is notoriously underreported in this kind of survey.) Prenatal alcohol use is thought to be responsible for at least 4,000 cases of mental retardation in the United States each year and perhaps ten times that number of ...