[8] As a child, Jensen was interested in herpetology and classical music, playing clarinet in the San Diego Symphony orchestra.

Later, Jensen was an important advocate in the mainstream acceptance of the general factor of intelligence, a concept which was essentially synonymous with his Level II conceptual learning.

Jensen claimed, on the basis of his research, that general cognitive ability is essentially an inherited trait, determined predominantly by genetic factors rather than by environmental conditions.

Jensen's most controversial work, published in February 1969 in the Harvard Educational Review, was titled "How Much Can We Boost IQ and Scholastic Achievement?"

[14][15][16] In 1994 he was one of 52 signatories on "Mainstream Science on Intelligence,"[17] an essay written by Linda Gottfredson and published in The Wall Street Journal, which declared the consensus of the signing scholars on the meaning and significance of IQ following the publication of the book The Bell Curve.

Jensen received $1.1 million from the Pioneer Fund,[18][19] an organization frequently described as racist and white supremacist in nature.

[1] According to David Lubinski of Vanderbilt University, the "extent to which [Jensen's] work was either admired or reviled by many distinguished scientists is unparalleled.

[26] Psychologist Sandra Scarr wrote in the journal Intelligence in 1998 that Jensen possessed an "uncompromising personal integrity" and set the standard for "honest psychological science".

She described his critics as "politically driven liars, who distort scientific facts in a misguided and condescending effort to protect an impossible myth about human equality".

Lisa Suzuki and Joshua Aronson of New York University wrote that Jensen had largely ignored evidence which failed to support his position that IQ test score gaps represent genetic racial differences.

[30] Paleontologist and evolutionary biologist Stephen Jay Gould criticized Jensen's work in his 1981 book The Mismeasure of Man.

Jensen also published a summary of the book the same year which was a target article in the journal Behavioral and Brain Sciences to which 27 commentaries were printed along with the author's reply.

John B. Carroll reviewed it favorably in 1982, saying it was a useful summary of the issues,[33] as did Paul Cline writing for the British Journal of Psychiatry.

The book deals with the intellectual history of g and various models of how to conceptualize intelligence, and with the biological correlates of g, its heritability, and its practical predictive power.

"[36] Douglas Detterman reviewed it in 2008 for Intelligence, writing that "the book would make a good introduction to the field of the measurement of individual differences in cognitive tasks for beginning graduate students.

"[37] Eric-Jan Wagenmakers and Han van der Mass, also writing for Intelligence in 2018, faulted the book for omitting the work by mathematical psychologists, advocating standardization of chronometric methods (which the authors consider problematic because it can hide method variance), and because it does not discuss topics such as the mutualism model of the g-factor and the Flynn effect.