The hereditarian view began to change in the 1920s in reaction to excessive eugenicist claims regarding abilities and moral character, and also due to the development of convincing environmental arguments.  In the 1940s many psychologists, particularly social psychologists, began to argue that environmental and cultural factors, as well as discrimination and prejudice, provided a more probable explanation of disparities in intelligence. According to Franz Samelson, this change in attitude had become widespread by then,  with very few studies in race differences in intelligence, a change brought out by an increase in the number of psychologists not from a "lily-white ... Anglo-Saxon" background but from Jewish backgrounds. Other factors that influenced American psychologists were the economic changes brought about by the depression and the reluctance of psychologists to risk being associated with the Nazi claims of a master race.  The 1950 race statement of UNESCO , prepared in consultation with scientists including Klineberg, created a further taboo against conducting scientific research on issues related to race.  Adolf Hitler banned IQ testing for being "Jewish" as did Joseph Stalin for being "bourgeois". 
Data from the 1983 and 1984 General Social Survey (J. A. Davis and T. W. Smith, 1988) were used to examine four explanations of Whites' opposition to residential integration. Results indicate that two forms of racism, fashioned prejudice and a sense of racial group position, consistently influenced opposition to residential integration. Class-based explanations had little explanatory power. Pragmatic objections, in this instance self-interested concerns, had small but equivocal effects. The value and ideological factors of political conservatism and individualism exerted a modest influence on Ss' attitudes on residential integration. Implications for developing more synthetic theories and understanding the social dynamics of race issues are discussed.