In 1956, Diana and Jacques Masson moved to Uruguay because Brunton believed that a third world war was imminent.

In 1970, Masson began studying to become a psychoanalyst at the Toronto Psychoanalytic Institute, completing a full clinical training course in 1978.

While perusing this material, Masson concluded that Freud might have rejected the seduction theory in order to advance the cause of psychoanalysis and to maintain his own place within the psychoanalytic inner circle, after a hostile response from the renowned sex-pathologist Richard von Krafft-Ebing and the rest of the Vienna Psychiatric Society in 1896 — "an icy reception from the jackasses," was the way Freud described it later to Fliess.

[7] In 1981, Masson's controversial conclusions were discussed in a series of New York Times articles by Ralph Blumenthal, to the dismay of the psychoanalytic establishment.

Masson was subsequently dismissed from his position as project director of the Freud Archives and stripped of his membership in psychoanalytic professional societies.

[9] Masson later wrote several books critical of psychoanalysis, including The Assault on Truth: Freud's Suppression of the Seduction Theory.

In the introduction to The Assault on Truth, Masson challenged his critics to address his arguments: "My pessimistic conclusions may possibly be wrong.

"[10] Janet Malcolm interviewed Masson at length when writing her long New Yorker article on this controversy, which she later expanded into In the Freud Archives, a book that also dealt with Eissler and with Peter Swales.

He also looked up the original places and documents in La Salpêtrière Hospital in Paris,[16] where Freud had studied with Charcot.

[17] Since the early 1990s, Masson has written a number of books on the emotional life of animals, one of which, When Elephants Weep, has been translated into 20 languages.

He has explained this radical change in the subject of his writings as follows: I'd written a whole series of books about psychiatry, and nobody bought them.

On the contrary, the meat, dairy, and egg industries all actively encourage us to give thought to our own immediate interest (taste, for example, or cheap food) but not to the real suffering involved ...

[19] Masson also wrote a book about living in New Zealand, including an interview with Sir Edmund Hillary.

[2] In the early 1990s, Masson had been engaged to University of Michigan feminist legal scholar Catharine MacKinnon, who wrote the preface to his A Dark Science: Women, Sexuality, and Psychiatry in the Nineteenth Century.