Scholars have identified errors and suspected data manipulation in Eysenck's work, and large replications have failed to confirm the relationships that he purported to find.

His mother was Silesian-born film star Helga Molander, and his father, Eduard Anton Eysenck, was an actor and nightclub entertainer who was once voted "handsomest man on the Baltic coast".

[14][15] Eysenck also created and developed a distinctive dimensional model of personality structure based on empirical factor-analytic research, attempting to anchor these factors in biogenetic variation.

Hans and Sybil Eysenck collaborated as psychologists for many years at the Institute of Psychiatry, University of London, as co-authors and researchers.

[24] In this book, Eysenck suggests that political behavior may be analysed in terms of two independent dimensions: the traditional left-right distinction, and how 'tenderminded' or 'toughminded' a person is.

Colleagues critiqued the research that formed the basis of this book, on a number of grounds, including the following: Eysenck advocated a strong influence from genetics and race on IQ differences.

Eysenck cited The IQ Controversy, the Media and Public Policy as showing that there was majority support for all of the main contentions he had put forward, and further claimed that there was no real debate about the matter among relevant scientists.

[30][31] Regarding this controversy, in 1988 S. A. Barnett described Eysenck as a "prolific popularizer" and he exemplified Eysenck's writings on this topic with two passages from his early 1970s books:[32] All the evidence to date suggests the ... overwhelming importance of genetic factors in producing the great variety of intellectual differences which we observe in our culture, and much of the difference observed between certain racial groups.the whole course of development of a child's intellectual capabilities is largely laid down genetically, and even extreme environmental changes ... have little power to alter this development.

[35] Scarr also criticised another statement of Eysenck on the alleged significantly lower IQs of Italian, Spanish, Portuguese and Greek immigrants in the US relative to the populations in their country of origin.

"[35]) Scarr writes that the careful reader would conclude that "Eysenck admits that scientific evidence to date does not permit a clear choice of the genetic-differences interpretation of black inferiority on intelligence tests," whereas a "quick reading of the book, however, is sure to leave the reader believing that scientific evidence today strongly supports the conclusion that US blacks are genetically inferior to whites in IQ.

[36][37] Eysenck also received funding for consultation research via the New York legal firm Jacob & Medinger, which was acting on behalf of the tobacco industry.

It was an investigation carried out with his student and associate Donald Prell, from 1948 to 1951, in which identical (monozygotic) and fraternal (dizygotic) twins, ages 11 and 12, were tested for neuroticism.

Eysenck and Prell concluded: "The factor of neuroticism is not a statistical artifact, but constitutes a biological unit which is inherited as a whole....neurotic predisposition is to a large extent hereditarily determined.

It is common practice in personality psychology to refer to the dimensions by the first letters, E and N. E and N provided a two-dimensional space to describe individual differences in behaviour.

Conversely, the extravert seeks to heighten his or her arousal to a more favourable level (as predicted by the Yerkes-Dodson Law) by increased activity, social engagement and other stimulation-seeking behaviours.

Linguist Siegfried Jäger [de] interpreted the preface to Krebs' book as having "railed against the equality of people, presenting it as an untenable ideological doctrine."

[61] In this introduction to Pearson's book, Eysenck retorts that his critics are "the scattered troops" of the New Left, who have adopted the "psychology of the fascists".

"[64] As Buchanan commented: Harder to brush off was the impression that Eysenck was insensitive, even willfully blind to the way his work played out in a wider political context.

[64] Eysenck described his views in the introduction to Race, Education and Intelligence: My recognition of the importance of the racial problem, and my own attitudes of opposition to any kind of racial segregation, and hatred for those who suppress any sector of the community on grounds of race (or sex or religion) were determined in part by the fact that I grew up in Germany, at a time when Hitlerism was becoming the very widely held doctrine which finally prevailed and led to the deaths of several million Jews whose only crime was that they belonged to an imaginary "race" which had been dreamed up by a group of men in whom insanity was mixed in equal parts with craftiness, paranoia with guile, and villainy with sadism.

Henry Gordon for example stated that Eysenck's viewpoint was "incredibly naive" because many of the parapsychology experiments he cited as evidence contained serious problems and were never replicated.

[70] Magician and skeptic James Randi noted that Eysenck had supported fraudulent psychics as genuine and had not mentioned their sleight of hand.

[72] According to Randi, "the authors instead gave users a highly biased procedure that would make experiments meaningless and certainly discourage further investigation by the amateur.

Citing Pelosi, psychologist David F. Marks wrote an open letter (also published in the Journal of Health Psychology) calling for the retraction or correction of 61 additional papers by Eysenck.

[citation needed] Eysenck said in 1990, "Note that I have never stated that cigarette smoking is not causally related to cancer and coronary heart disease; to deny such a relationship would be irresponsible and counter to the evidence.

In his statement at the time, Eysenck failed to take into account the highly addictive effect of nicotine, which was only later clearly proven by neurophysiological studies.

[82][non-primary source needed] Grossarth emphasized that the development of disease is often multicausal, whereby the factors reinforce each other in their effect, and he explicitly speaks of behavioral characteristics that may change due to psychological intervention.

[81] Following the King's College London enquiry the International Journal of Sport Psychology retracted a paper that was coauthored by Eysenck in 1990.

[85] Some of these are early papers having nothing to do with health and the King's College enquiry "did not specifically name the articles this expression of concern relates to as problematic".