Dermo-optical perception (DOP) — also known as dermal vision, dermo-optics, eyeless sight, eyeless vision, skin vision, skin reading, finger vision, paroptic vision, para-optic perception, cutaneous perception, digital sight, and bio-introscopy — is a term that is used in parapsychological literature to denote the alleged capability to perceive colors, differences in brightness, and/or formed images through the skin (without using the eyes, as distinct from blindsight), especially upon touching with the fingertips.
Typically, people who claim to have dermo-optical perception claim to be able to see using the skin of their fingers or hands. People who claim to have DOP often demonstrate it by reading while blindfolded. The effect has not been demonstrated scientifically.
The first Western scientific reports are from the 17th century. Scattered cases kept being reported over the years, but scientific interest didn't pick up until the 20th century. ESP researchers enthusiastically studied DOP, hoping that it was an example of extra-sensory perception, but they could only conclude that some of the results couldn't be explained by cheating.
According to Joe Nickell, a noted skeptic, many circus entertainers and magicians have utilized tricks to perform eyeless-sight feats. In the 1880s Washington Irving Bishop performed the "blindfold drive" with a horse-drawn carriage. In the early 20th century Joaquín María Argamasilla known as the "Spaniard with X-ray Eyes" claimed to be able to read handwriting or numbers on dice through closed metal boxes. Argamasilla managed to fool Gustav Geley and Charles Richet into believing he had genuine psychic powers. In 1924 he was exposed by Harry Houdini as a fraud. Argamasilla peeked through his simple blindfold and lifted up the edge of the box so he could look inside it without others noticing.
A teenager from America named Pat Marquis known as "the boy with X-ray eyes" was tested by J. B. Rhine and was caught peeking through the blindfold down his nose. Science writer Martin Gardner has written that the ignorance of blindfold deception methods has been widespread in investigations into objects at remote locations from persons who claim to possess eyeless vision. Gardner documented various conjuring techniques psychics such as Rosa Kuleshova, Linda Anderson and Nina Kulagina have used to peek from their blindfolds to deceive investigators into believing they used eyeless vision.
In 2010, an Italian lady known as R. G. who claimed she could peer inside sealed boxes with X-ray vision to describe what is inside was tested at the University of Pavia by Massimo Polidoro, chemist Luigi Garlaschelli and physicist Adalberto Piazzoli. Twelve objects were selected and placed in wooden boxes. She failed the test, getting only one object correct.
Joe Nickell who has studied DOP has written "To date, no one has demonstrated convincingly, under suitably controlled conditions, the existence of X-ray sight or any other form of clairvoyance or ESP."
Experiments into DOP by scientists have shown no effect. Alleged positive results haven't been accepted by the mainstream scientific community due to procedures not being tight enough to prevent cheating by participants, problems with replicating the effect reliably, and concerns about the colors being recognized by the texture of the ink on the paper (people who are blind from an early age can recognize Braille patters that only have .2 millimeters of elevation above the paper, and the limit of relief distinction in fingers is still unknown). In summary, DOP has not been demonstrated scientifically.
Most of DOP positive results have been explained as cheating by participants, either via the use of magicians' tricks, or via "peeking down the nose" (cheating by participants) In recent years, DOP has been the object of mainstream research that had no links with ESP.
Apart from trickery, there are several hypotheses about how fingers could "see" radiation emitted by the colors in the paper, but none have been tested successfully. For example, people can hold their fingers near to painted and non-painted surfaces, and distinguish them by how much corporal heat is radiated back to their fingers. While it has not been verified if fingers can be sensitive enough to detect heat radiation from different inks in paper, it is theorized that blind people could plausibly do it.
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