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of the body’s position and even its existence. Such immersion chambers could produce
“altered states” much more profound than those described in the original experiments.
At the time, such sensory deprivation tanks were sought out as avidly as (and sometimes
combined with) “consciousness-expanding” drugs, which were more widely available
then. 1
There was a great deal of research on sensory deprivation in the 1950s and 1960s (a
1969 book edited by Zubek entitled Sensory Deprivation: Fifteen Years of Research listed
thirteen hundred references)—but then scientic interest, like popular interest, started
to peter out, and there was relatively little research until the recent work of Alvaro
Pascual-Leone and his colleagues (Merabet et al.), who designed a study to isolate the
eects of pure visual deprivation. Their subjects, though blindfolded, were able to move
around freely and “watch” TV, listen to music, walk outside, and talk to others. They
experienced none of the somnolence, boredom, or restlessness the earlier test subjects
had shown. They were alert and active during the daytime, when they carried tape
recorders so they could take immediate note of any hallucinations. They enjoyed calm,
restful sleep at night, and each morning they dictated what they could remember of their
dreams—dreams that did not seem significantly altered by their being blindfolded.
The blindfolds, which allowed the subjects to close or move their eyes, were worn
continuously for ninety-six hours. Ten of the thirteen subjects experienced
hallucinations, sometimes during the rst hours of blindfolding, but always by the
second day, whether their eyes were open or not.
Typically the hallucinations would appear suddenly and spontaneously, then
disappear just as suddenly after seconds or minutes—although in one subject,
hallucination became almost continuous by the third day. The subjects reported a range
from simple hallucinations (ashing lights, phosphenes, geometrical patterns) to
complex ones (gures, faces, hands, animals, buildings, and landscapes). In general, the
hallucinations appeared full-fledged, without warning—they never seemed to be built up
slowly, piecemeal, like voluntary imagery or recall. For the most part, the hallucinations
aroused little emotion and were regarded as “amusing.” Two subjects had hallucinations
which correlated with their own movements and actions: “I have the sensation that I can
see my hands and my arms moving when I move them and leaving an illuminated trail,”
said one subject. “I felt like I was seeing the pitcher while I was pouring the water,” said
another.
Several subjects spoke of the brilliance and colors of their hallucinations; one
described “resplendent peacock feathers and buildings.” Another saw sunsets almost too
bright to bear and luminous landscapes of extraordinary beauty, “much prettier, I think,
than anything I have ever seen. I really wish I could paint.”
Several mentioned spontaneous changes in their hallucinations; for one subject, a
buttery became a sunset, which changed to an otter and, nally, a ower. None of the
subjects had any voluntary control over their hallucinations, which seemed to have “a
mind” or “a will” of their own.
No hallucinations were experienced when subjects were engaged in challenging
sensory activity of another mode, such as listening to television or music, talking, or