Dutch psychical researcher whose career ended amid charges of large-scale fraud. Tenhaeff joined the Studievereniging Voor Psychical Research (SVPR) soon after its founding and in 1928 became a cofounder of the Tijdschrift voor Parapsychologie. All parapsychological research stopped during the Nazi occupation, but Parapsychology was reestablished in the Netherlands soon after the war ended. Tenhaeff emerged as the dominant force in the SVPR. About the same time, he discovered Gerard Croiset, who after a brief array of tests was pronounced a remarkable psychic. Tenhaeff not only tested Croiset but worked with him on sharpening and improving his ability. He also encouraged the use of Croiset’s abilities in a variety of practical ways, most importantly in assisting police in solving crimes and finding lost children. Tenhaeff publicized Croiset’s successes nationally and internationally.
In 1953, Tenhaeff was appointed to the newly established chair in parapsychology at the University of Utrecht, one of the few full-time academic positions in the held. He was also named director of the University’s Parapsychology Institute. Croiset joined him near Utrecht in 1956. Among the more notable of the demonstrations of Croiset’s abilities conducted by Tenhaeff were the “chair tests. Croiset was asked to describe the person who would sit in a specific chair at a future meeting. Croiset’s predictions were sealed and opened at the meeting and his description compared with the person in the chair.