It has been known for a while that for example African-Americans score on average lower in IQ tests than European-Americans. Usually it is said that average score for African-Americans is 85, one standard deviation (SD) below European-Americans (100). However, in Europe there is one group who score two SDs below continental average, and as much as one SD below African-Americans. These are the Roma, whose average IQ score (at least for Balkan Gypsies) is perhaps as low as 70, much lower than African-American: http://www.sciencedirect.com/science/article/pii/S0160289606001097 Low average Roma IQ correlates with their social problems across Europe, but it is hard to say which is the cause and which is the effect: Documentary on the Roma people in Bulgaria: Link to video. Short documentary on the Roma in Slovakia: Link to video. Roma people in Britain - On Benefits & Proud: Link to video. So, what are the possible causes of such low (much lower than African-American) average IQ scores among European Gypsies? And what is the cause-effect relation between their problems and their IQ scores, if there is one. Do their poverty and their social problems cause their low performance in IQ tests, or inversely?