Everybody knows about psychological tests that can measure the level of our intelligence, or so-called IQ-tests. Author of the first such test was Hans Jurgen Eysenck (1916 -1997), British psychologist and one of the leaders of biological paradigm in psychology of XXth century. He was also creator of factor theory of personality.
But despite of the popularity of his IQ-test around the world, several studies of Eysenck were perceived as "terrible and shocking racist thoughts". Perhaps, these ideas were quite normal for Nazi Germany but in Europe after WW II they were unacceptable. There a several interesting facts about how was IQ-test created, and what was put in the ground of its theory.
Eyshenk studied the psychological variability among people of different races. In particular, he suggested that white people have more IQ than black people on average by 15%. After such conclusions, American booksellers refused to print and sell his book "The IQ Argument”, 1971. To buy this book in the U.S.A. in the 1970s was also unreal. American media in those years even have refused to publish any reviews on it.
Studies of basic personality inspired Eysenck to begin an analysis of the results of the psychiatric examination of the contingent of US soldiers. Among them were groups of psychic unhealthy men and that were specified as neurotics. As a result of his analysis, it has been allocated 39 variables for which data groups differed significantly. That factor analysis yielded other four factors, which included such as extraversion, introversion and neuroticism (the work «Dimensions of Personality», 1947). As a theoretical framework Eysenck based on psychodynamic understanding of personality features as genetically caused, and finally, biochemical.