We have all been pretty conditioned these last several years to view food additives of any sort as pure negatives. So it’s interesting to look back to an earlier time and see the effect of an additive that practically no one can argue with. James Feyrer, Dimitra Politi, and David Weil have written a new working paper (abstract; PDF from 2008) about the effect of adding iodine to table salt:
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 U.S. 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 WWI and WWII to compare outcomes of cohorts born before and after iodization, in localities that were naturally poor and rich in iodine. We find that for the one-quarter of the population most deficient in iodine this intervention raised IQ by approximately one standard deviation. Our results can explain roughly one decade’s worth of the upward trend in IQ in the U.S. (the Flynn Effect). We also document a large increase in thyroid related deaths following the countrywide adoption of iodized salt, which affected mostly older individuals in localities with high prevalence of iodine deficiency.
Iodine is hardly the only beneficial additive in our food supply. There’s vitamins A and D in milk. And fluoride in the water? None of these are completely without controversy of course. What other mostly beneficial additives can you think of?
A new British study has found that people who scored well on IQ tests as children are more likely to be drug users as adults, especially women. Authors James White and G. David Batty published their study online in the Journal of Epidemiology and Community Health, and looked at data from almost 8,000 people over several decades to test what habits and qualities are tied to drug use.
The results suggest that men with high IQ scores at 5 years-old are 50 percent more likely to use drugs by the age of 30 than those with low IQ scores. High IQ scoring women at 5 years-old are twice as likely to use drugs than their low IQ counterparts. Read More »
Last spring, we posted on Phil Tetlock’s massive prediction tournament: Good Judgment. You might remember Tetlock from our latest Freakonomics Radio podcast, “The Folly of Prediction.” (You can download/subscribe at iTunes, get the RSS feed, or read the transcript here.)
Tetlock is a psychologist at the University of Pennsylvania, well-known for his book Expert Political Judgment, in which he tracked 80,000 predictions over the course of 20 years. Turns out that humans are not great at predicting the future, and experts do just a bit better than a random guessing strategy. Read More »
See ADDENDUM (8-3-11; 9:13am EDT) below
Read More »
Over a period of around four weeks, the company gave a Wechsler Adult Intelligence Scale (WAIS) to users looking for free online IQ assessment tests, then recorded the results and browsers used for all participants above the age of 16.
Across the board, the average IQ scores presented for users of Internet Explorer versions 6 through 9 were all lower than the IQ scores recorded for Firefox, Chrome, Safari, Camino, and Opera users.