Marion was investigated by members of the Society for Psychical Research in the late 1930-1940s.
He was tested by the parapsychologist Samuel Soal at the National Laboratory of Psychical Research in a series of experiments who attributed his success not to paranormal power but to the expert ability of picking up subtle visual clues from his audience.
Soal also claimed that members of The Magic Circle were able to duplicate Marion's feat of identifying playing cards.
Psychologist Andrew Neher has written that "Marion could identify which of a number of small cans contained an object; he did this by noting the involuntary reactions of observers who knew which can the object was in."

He was investigated by Harry Price who concluded his abilities were the result of hyperesthesia, not the paranormal.

Marion was tested by the psychical researchers R. H. Thouless and Bertold Wiesner who rejected Soal's conclusions.
From their experiments they claimed to be convinced that he possessed psychic powers.
Their views were summarized in the foreword to Marion's autobiography In My Mind's Eye (1950).

Magician Milbourne Christopher once worked with Marion at one of his performances and observed his methods.
Christopher had no reason to believe he had genuine psychic powers.
He wrote that Marion was an expert mentalist who could pick up clues from his audience's "changes in breathing, tensions and relaxations, and varying positions of the fingers, hands of the fingers, hands, and feet of his subject when he works without contact."
Marion was investigated by members of the Society for Psychical Research in the late 1930-1940s. He was tested by the parapsychologist Samuel Soal at the National Laboratory of Psychical Research in a series of experiments who attributed his success not to paranormal power but to the expert ability of picking up subtle visual clues from his audience. Soal also claimed that members of The Magic Circle were able to duplicate Marion's feat of identifying playing cards. Psychologist Andrew Neher has written that "Marion could identify which of a number of small cans contained an object; he did this by noting the involuntary reactions of observers who knew which can the object was in."
He was investigated by Harry Price who concluded his abilities were the result of hyperesthesia, not the paranormal.
Marion was tested by the psychical researchers R. H. Thouless and Bertold Wiesner who rejected Soal's conclusions. From their experiments they claimed to be convinced that he possessed psychic powers. Their views were summarized in the foreword to Marion's autobiography In My Mind's Eye (1950).
Magician Milbourne Christopher once worked with Marion at one of his performances and observed his methods. Christopher had no reason to believe he had genuine psychic powers. He wrote that Marion was an expert mentalist who could pick up clues from his audience's "changes in breathing, tensions and relaxations, and varying positions of the fingers, hands of the fingers, hands, and feet of his subject when he works without contact."
Frederick Marion