That Jews are and have been over-represented in areas of high accomplishment has been known for some time -- in intellectual achievement, science, medicine, law, academia, business and finance, and politics. In 2007, for example, the Washington Postreported that Jewish presence in the U.S. Congress four times greater than their presence in the public at large. The race and IQ theorist La Griffe du Lion has estimated that among the most g-loaded professions -- that is, those professions that requite the greatest intelligence in which to perform well, such as Supreme Court law clerks and elite college faculty -- the proportion of Jews approaches 30 percent, in contrast to their proportion of the American population at around two percent. Jews appear in the ranks of Nobel Laureates at some six times the level that would be expected from their share of the population.
Almost since Jewish intellectual achievement has been noticed, observers have speculated on the reasons. In 1919, Thorstein Veblen wrote about the intellectual preeminence of the Jews in modern Europe, attributing said preeminence to high intelligence. Others have theorized that Jews value study, or intellect, or success more than non-Jews, and that these are the sources of their accomplishment. It's been contended that study of sacred texts as a Jewish traditional value has somehow translated into higher accomplishment.
The intelligence researcher Richard Lynn of the University of Ulster, together with the evolutionary psychologist Satoshi Kanazawa of the London School of Economics, decided to take a look at this issue. They did so through the General Social Survey (GSS), a survey undertaken annually of several thousand people in the U.S. The survey asks questions about values, and additionally administers a short vocabulary test which can be used as a proxy for IQ. Lynn and Kanazawa found that the vocabulary tests indicated that Jews possessed IQs on average 9 points higher than non-Jews, and also found that the values of Jews and non-Jews did not differ significantly.
[T]he results do not provide any evidence for the theory that Jews attach more importance to success or to studiousness than non-Jews. In fact Jews attach less importance to success and to studiousness than non-Jews in the results set out in both Tables 1 and 2, although the differences between Jews and non-Jewish are not statistically significant.
Jews do not differ much from others in the values they would most like their children to have. Jews and non-Jews attach most importance to their children having good judgment, being considerate, honest and responsible, and Jews and non-Jews attach least importance to their children valuing cleanliness and appropriate sex role behaviour.
[T]he results clearly support the high intelligence theory of Jewish achievement while at the same time provide no support for the cultural values theory as an explanation for Jewish success.
There you have it: not completely definitive, but "the results clearly support the high intelligence theory of Jewish achievement", with "no support for the cultural values theory".
Perhaps one reason for ongoing confusion is that people do what they are good at. For instance, IQ and years of education are positively correlated, and its not because education increases IQ; rather, it's the other way around.
Cochran, Hardy, and Harpending, in their Natural History of Ashkenazi Intelligence, theorized that the higher average intelligence of Ashkenazi Jews is a product of recent evolution. However, the Sephardi Jews of medieval and early modern Spain were also known as high achievers, so much so that laws were enacted that required high office holders and members of the professions to prove non-Jewish lineage. (It should probably be emphasized that to my knowledge no statistics on Sephardi achievement exist for that era.) If the Sephardi Jews did in fact achieve more in relation to their fraction of the population, then either the thesis of Cochran et al. applies to more than just the Ashkenazis, in which case it might need modification, or Sephardi Jews did indeed have different values than the non-Jewish population; the latter would indicate that Jewish values have been responsible for their success, at least at some times and in some places. The proverbial sobriety of Jews in Eastern Europe compared to the drunkenness of their Polish and Russian neighbors, it seems to me, must have been in some way advantageous. So, while Lynn and Kanazawa's results clearly support high intelligence and not values as being the source of Jewish success, perhaps this has not applied always and everywhere.