Iodized salt is so common today that you may never have considered the two as separate elements. This wasn’t always the case -- in 1924 iodized salt was first sold commercially in the U.S. to reduce the incidence of goiter – or swelling of the thyroid gland. Within a decade the average I.Q. in the United States had risen three and a half points. In areas that had been iodine deficient, I.Q. levels rose an average of fifteen points. A new paper from the National Bureau of Economic Research traces this leap in I.Q. back to iodized salt. We spoke with Max Nisen, war room reporter for Business Insider, where he wrote about I.Q. increases as a result of iodized salt.