[7] In 1976, Epstein enrolled in the Master's program of Community and Clinical Psychology at the University of Maryland, Baltimore County.

While at graduate school, Epstein personally reached out to the then-retired B.F. Skinner, and convinced him to begin pigeon research again at the Psychology Department at Harvard University.

[17] For six years, he was also a researcher and Associate Investigator at the Center for Behavioral Epidemiology, Graduate School of Public Health, San Diego State University.

[25] In 2013, he moved to the Fiji Islands to serve as the first full Professor of Psychology at the University of the South Pacific, a position he held until 2015.

[26][27] An autobiographical essay documenting his long involvement with the media was published in 2006 in the academic journal Perspectives on Psychological Science.

[34] His theory is based in part on research he has conducted on how love arises in arranged marriages in multiple cultures worldwide.

[40][41][42][43] Epstein has conducted large-scale studies on sexual orientation that confirm assertions made by Sigmund Freud, Alfred Kinsey, and others that (a) sexual orientation lies on a continuum, (b) bisexuality is the natural norm for human beings, and (c) most people claim to be straight because of social pressure.

Evidence collated in the paper suggested that the implementation of CSP would dramatically slow the spread of the virus even if compliance with the plan was only moderate.

[81][82] He published these findings in the peer-reviewed scientific journal Proceedings of the National Academy of Sciences,[83] and continues to research this phenomenon.

[84][85] His research led to him being invited to testify before the United States Senate Judiciary Subcommittee on the Constitution, hearing on Google and Censorship, in June 2019.

[87][88] He has expressed concern that this effect could be used by Big Tech companies to influence peoples' opinions with impunity.

[92] Epstein has been an outspoken critic of Google and has proposed methods for reducing the threat that Big Tech poses to free-and-fair elections.

[93][94] In 2012, he said that Google could rig the 2016 United States presidential election and that search engine manipulation was "a serious threat to the democratic system of government".

Safiya Noble cited Epstein's research about search engine bias in her 2018 book Algorithms of Oppression,[99] although she has expressed doubt that search engines ought to counter-balance the content of large, well-resourced and highly trained newsrooms with what she called "disinformation sites" and "propaganda outlets".

[100] Ramesh Srinivasan, a professor of information studies at UCLA focusing on "the relationships between technology and politics", agreed with Epstein that "the larger issue" of how search engines can shape users' views is "extremely important", but questioned how many undecided voters are using Google to help them decide whom to vote for.

[103] His wife Misti was killed in a car accident in 2019, shortly after Epstein testified before Congress regarding Google Search, ending a marriage that began in 2012.