The list includes metro areas of 1 million or more people, divided on a per-capita basis. The criteria included both education levels and intellectual environment. Here's more, from The Daily Beast:
The education half encompassed how many residents had bachelor's degrees (35 percent weighting) and graduate degrees (15 percent). No credit was given for "some college," or "some grad school"--we rewarded those who finished the race. The intellectual environmental half had three subparts. First, we looked at nonfiction book sales (25 percent), as tracked by Nielsen BookScan, the nation's leading provider of accurate point-of-sale data, which tracks roughly 300,000 titles each week. ... We also measured the ratio of institutions of higher education (15 percent), as defined by the federal government--different than just measuring college degrees, this acknowledges that universities don't just churn out diplomas, but instead drive the intellectual vigor of cities. Finally, many studies link intelligence and political engagement, so we weighed this, too, as measured by the percentage of eligible voters who cast ballots in the last presidential election (10 percent). (Our relatively small weighting acknowledges that numerous other local factors can affect turnout.)
Once we had all these comparable, per-capita figures, we ranked the cities in each category, assigning 10 points to those near the very top, and 0 to the bottom, with scores allocated between in a broad bell curve. We then added the totals, and multiplied by two, which made for a perfect score of 200, a wash-out score of 0, and an average score right at 100--close to the exact parameters of a classic IQ test.
Memphis, which earned an IQ score of just 48, was given low marks for nonfiction book sales as well as low rates of college graduation.