Dermo-optical Perception

      Dermo-optical perception (DOP) is 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.  These terms are used to denote the alleged capability to perceive colors, differences in brightness, and formed images through the skin without using the eyes. This is usually done by touching with the fingertips. 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.
      Scientific interest didn't pick up until the 20th century.  ESP researchers 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.  Magazines reported on several cases calling them "X-ray wonders", but all of them were found to be cheating when tested under controlled conditions. Studies done by Western scientists showed no effect, while studies done by Eastern scientists always showed this effect.The positive results have not been accepted because their procedures were probably not tight enough to prevent cheating by participants. Also, the lack of proper documentation doesn't allow to check if the controls were good enough.  There are also problems with replicating the effect reliably, and concerns about the colors being recognized by the texture of the ink on the paper.
       In conclusion, DOP is still not proven scientifically.  Most of DOP positive results have been explained as cheating by participants, either by the use of magicians' tricks, or by "peeking down the nose^." Some of the results can't be explained by cheating. Recently, DOP has been the object of "mainstream" research that had no links with ESP.  Besides the "cheating" explanation, there are several theories about how fingers could "see" radiation given off by the colors in the paper, but none has been tested successfully. For example, people can hold their fingers near painted and non-painted surfaces, and distinguish them by how much 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 possibly do it. The low quality of many studies, the cheating, the discovery that the most famous cases were fraud, and the use by ESP proponents have caused DOP to be classified as pseudoscience and to be dismissed as baseless paranormal claims.