However, I find that the book got a bit more predictable and dragging a little past the halfway mark. I felt he dwelt too much on what was already obvious by that time.

This is consistent with their performance on math/science subjects. Seligman also notes possible explanations of this including:

“Severely compressed, his explanation goes about like this: Some sixty thousand years ago, when the lee Age descended on the Northern Hemisphere, the Mongoloid populations faced uniquely hostile “selection pressure” for greater intelligence. Northeast Asia during the Ice Age was the coldest part of the world inhabited by man. Survival required major advances in hunting skills. Lynn’s 1987 paper refers to “the ability to isolate slight variations in visual stimulation from a relatively featureless landscape, such as the movement of a white Arctic hare against a background of snow and ice; to recall visual landmarks on long hunting expeditions away from home and to develop a good spatial map of an extensive terrain.” These, Lynn believes, were the pressures that ultimately produced the world’s best visuospatial abilities.”

Also, Gladwell’s explanation for Jewish legal success on working in the garment industry in NYC isn’t convincing. Seligman notes jewish performance on the verbal component of psychometric tests is above average. The Cochran/Harpending paper on Ashkenazi Jewish intelligence suggests this is partly genetic. See Charles Murray’s commentary on the paper:

“Assessing the events of the 1st century C.E. thus poses a chicken-and-egg problem. By way of an analogy, consider written Chinese with its thousands of unique characters. On cognitive tests, today’s Chinese do especially well on visuo-spatial skills. It is possible, I suppose, that their high visuo-spatial skills have been fostered by having to learn written Chinese; but I find it much more plausible that only people who already possessed high visuo-spatial skills would ever devise such a ferociously difficult written language. Similarly, I suppose it is possible that the Jews’ high verbal skills were fostered, through secondary and tertiary effects, by the requirement that they be able to read and understand complicated texts after the 1st century C.E.; but I find it much more plausible that only people who already possessed high verbal skills would dream of installing such a demanding requirement.”

http://www.commentarymagazine.com/…/jewish-genius-10855