Sensory leakage

Sensory leakage is a term used to refer to information that transferred to a person by conventional means (other than Psi) during an experiment into Psi.

For example, where the subject in an ESP experiment receives a visual cue — the reflection of a Zener card in the holder's glasses — sensory leakage can be said to have occurred.

Scientists such as Donovan Rawcliffe (1952), C. E. M. Hansel (1980), Ray Hyman (1989) and Andrew Neher (2011) have studied the history of psi experiments from the late 19th century up until the 1980s. In every experiment investigated flaws and weaknesses were discovered so the possibility of naturalistic explanations (such as sensory cues) or deception and trickery were not ruled out. The data from the Creery sister and the Soal-Goldney experiments were proven to be fraudulent, one of the subjects from the Smith-Blackburn experiments confessed to fraud, the Brugmans experiment, the experiments by John E. Coover and those conducted by Joseph Gaither Pratt and Helmut Schmidt did not rule out the possibility of sensory cues or trickery.

In the 20th century J. B. Rhine carried out experiments into ESP. His experiments were discredited due to the discovery that sensory leakage or cheating could account for all his results such as the subject being able to read the symbols from the back of the cards and being able to see and hear the experimenter to note subtle clues.Terence Hines has written:

The methods the Rhines used to prevent subjects from gaining hints and clues as to the design on the cards were far from adequate. In many experiments, the cards were displayed face up, but hidden behind a small wooden shield. Several ways of obtaining information about the design on the card remain even in the presence of the shield. For instance, the subject may be able sometimes to see the design on the face-up card reflected in the agent’s glasses. Even if the agent isn’t wearing glasses it is possible to see the reflection in his cornea.

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