The 1920s and 1930s witnessed the publication of a number of British research projects on the comparative intelligence of Jews and non-Jews. These studies, which mostly involved the testing of schoolchildren, were not solely intended for academic discussion but were also invested with political meaning. In a period of substantial Jewish immigration to Britain, studies of this kind were often seen as potential sources of evidence, both by those who wished to defend the Jewish influx and those who wished to curtail it. Schaffer considers three studies of Jewish/non-Jewish intelligence in an attempt to illuminate some of the ideas and beliefs that underpinned research into racial mental difference in the inter-war years. He questions the tendency of some historians to see this period as a time of change in British racial studies, and explores the extent, nature and meaning of those changing scientific racial methodologies and ideas that were evident. Most importantly, he interrogates the popular argument that the presentation of Jewish intelligence as equal or superior to that of other Britons was necessarily a challenge to race science. Instead, he argues that positive perceptions of Jewish racial mental difference could and did sit comfortably within the parameters of traditional racial analysis. By exploring the thinking behind assessments of Jewish intelligence difference, Schaffer highlights the influence of pre-existing racial stereotypes in shaping research agendas and results. He also considers the role of the British Jewish community in funding and challenging studies of Jewish intelligence, arguing that the community's defensive strategy against negative racial labelling was the cause of discord and change during this period.