Do Jewish people have better cognitive abilities than average population? Jewish people are overrepresented in politics and science especially in the United States. Do they have better cognitive abilities than average population? If yes, what is the reason for this?

Statistics:


0.2% of world population is Jewish
About 1.7% - 2.6% of Americans are Jewish
10% of US senators are Jewish
About 23% of Nobel prize winners are Jewish.
Your explanation limits your question to the present day United States. Richard Lynn (2004) indeed found that American Jews have a higher verbal intelligence than non-Jewish whites by an average of 7.5 IQ points. But since American Jews are largely descendants of European immigrants, their higher relative intelligence might be a result of so-called "eugenic practices" (Zeidner, 2012): many highly intelligent Jews (e.g. scientists and artists) received special help from foreign parties to flee the Nazi holocaust, and those that where wealthy (presumably because they were more intelligent) had better resources, e.g. to bribe German officials (which is documented) or simply to pay for their transportation. From the current situation in the US it is therefore unclear if Jews are hereditary more intelligent or other factors have influenced the selection of Jewish American immigrants, if compared to the descendants of non-Jewish immigrants, many of which where poor (and uneducated). As other studies show (e.g. http://en.wikipedia.org/wiki/IQ_and_the_Wealth_of_Nations), intelligence is influenced by food (= wealth) and education (= wealth) by about 10 IQ points. So the higher intelligence of American Jews lies within what those factors might explain.

Taking a wider view, there are other studies that find higher intelligence in Jews as far back as the middle ages or in other areas of the world also. The debate is summarized in a Wikipedia article as well as countless articles on the web.

Sources:


Lynn, R. (2004). The intelligence of American Jews. Personality and Individual Differences, 36(1), 201-206.
Zeidner, M. (2012). The Chosen People: A Study of Jewish Intelligence and Achievement (Review). Times Higher Education. Available online at http://www.timeshighereducation.co.uk/books/the-chosen-people-a-study-of-jewish-intelligence-and-achievement/418945.article