prosopopesis
A sudden and profound change of an individual's personality, whether spontaneous or induced e.g. in hypnosis.
rare
Mr. Soal declares that while the presence of certain persons is favorable to his duplication of personality and while some persons actually aid the prosopopesis, others have an inhibitive influence.
Where it comes from
From prosopo- (“person, mask”) + -poiesis; introduced by French psychical researcher René Sudre, whose book "Parapsychology" (1926) was published in English by Grove Press in 1962. Possibly influenced by προσωποποιία (prosōpopoiía, “dramatization, prosopopoeia”).
Adapted from the Wiktionary entry prosopopesis (CC BY-SA 4.0).