You don’t need psychedelic drugs to start seeing colors and objects that aren’t really there. Just 15 minutes of near-total sensory deprivation can bring on hallucinations in many otherwise sane individuals.
Psychologists stuck 19 healthy volunteers into a sensory-deprivation room, completely devoid of light and sound, for 15 minutes. Without the normal barrage of sensory information flooding their brains, many people reported experiencing visual hallucinations, paranoia and a depressed mood.
“This is a pretty robust finding,” wrote psychiatrist Paul Fletcher of the University of Cambridge, who studies psychosis but was not involved in the study. “It appears that, when confronted by lack of sensory patterns in our environment, we have a natural tendency to superimpose our own patterns.”
The findings support the hypothesis that hallucinations happen when the brain misidentifies the source of what it is experiencing, a concept the researchers call “faulty source monitoring.”
“This is the idea that hallucinations come about because we misidentify the source of our own thoughts,” psychologist Oliver Mason of the University College London wrote in an e-mail to Wired.com. “So basically something that actually is initiated within us gets misidentified as from the outside.” Mason and colleagues published their study in October in the Journal of Nervous and Mental Disease.