[1] He was the first to introduce the link between past experiences and present-day disturbances and was noted for his studies involving induced somnambulism.

[9] Janet was one of the first people to allege a connection between events in a subject's past life and their present-day trauma, and coined the words "dissociation"[10] and "subconscious".

[12] The 20th century saw Janet developing a grand model of the mind in terms of levels of energy, efficiency and social competence, which he set out in publications including Obsessions and Psychasthenia (1903) and From Anguish to Ecstasy (1926), among others.

[15] Janet established a developmental model of the mind in terms of a hierarchy of nine "tendencies" of increasingly complex organisational levels.

"[citation needed] Controversy over whose ideas came first, Janet's or Sigmund Freud's, emerged at the 1913 Congress of Medicine in London.

[24] He stated further that "we followed his example when we took the splitting of the mind and dissociation of the personality as the centre of our position", but he was also careful to point out where "the difference lies between our view and Janet's".

In his lectures of 1915-16, Freud said that "for a long time I was prepared to give Janet very great credit for throwing light on neurotic symptoms, because he regarded them as expressions of idées inconscientes which dominated the patients".

Alfred Adler openly derived his inferiority complex concept from Janet's Sentiment d'incomplétude,[37] and the two men cited each other's work on the issue in their writings.

Of his great synthesis of human psychology, Henri Ellenberger wrote that "this requires about twenty books and several dozen of articles".