Under hypnosis, a link between numbers and colors can be suggested, which can continue even after hypnosis. Photo: Membeth
Reading aloud Under hypnosis, some people begin to see colors when reading letters and numbers, though otherwise they are not synesthetes. This has been proven by scientists from University College London. Under the direction of Roi Cohen Kadosh, the researchers even managed that some subjects inextricably linked numbers and colors even after the end of hypnosis. For example, the participants always perceived the number one in red. The researchers therefore believe that synesthesia is not based on an innate peculiarity in the brain, but can also be triggered by disinhibition processes. In synesthesia, various sensory perceptions can be coupled with each other. Thus, some synesthetes not only perceive sounds acoustically, but automatically associate forms or tastes with them. Often this phenomenon occurs from birth on. However, Kadosh and his colleagues also report cases in which sufferers suddenly developed synaesthetic abilities following brain damage.

Which processes in the brain are responsible for synesthesia, is so far disputed among researchers. Some scientists, for example, believe that synaesthetes are more closely related to different brain areas. Another group of researchers, including Kadosh, believes that different degrees of blockage within the brain are critical for synesthesia.

To test their assumption, the scientists hypnotized volunteers. The assumption behind this was that the blocking processes are loosened by the hypnosis. During the hypnosis, the scientists therefore suggested to the subjects a combination of colors and numbers. For some participants, they persisted with a posthypnotic command, even after the end of the actual hypnosis. These participants then showed similar symptoms as synesthetes: they could not correctly recognize a black printed one against a red background, since the number one had also been marked as red during hypnosis. Kadosh and his colleagues see this as proof that no special connections in the brain are needed for synesthesia.

Roi Cohen Kadosh (University College London) et al .: Psychological Science, Vol. 19, No. 10. ddp / science.de? Markus Zen's ad

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