Hallucinations

While these images first appeared as if projected onto a flat screen, after a time they became “compellingly three-dimensional” for some of the subjects, and parts of a scene might become inverted or pivot from side to side.

After being initially startled, the subjects tended to find their hallucinations amusing, interesting, or sometimes irritating (“their vividness interfered with sleep”) but without any “meaning.” The hallucinations seemed external, proceeding autonomously, with little relevance or reference to the individual or situation. The hallucinations usually disappeared when the subjects were asked to do complex tasks like multiplying three-figure numbers, but not if they were merely exercising or talking to the researchers. The McGill researchers reported, as many others have, auditory and kinesthetic hallucinations as well as visual ones.

This and subsequent studies aroused enormous interest in the scientific community, and both scientific and popular efforts were made to duplicate the results. In a 1961 paper, John Zubek and his colleagues reported, in addition to hallucination, a change in visual imagery in many of their subjects:

At various intervals … the subjects were asked to imagine or visualize certain familiar scenes, for example, lakes, countryside, the inside of their homes, and so forth. The majority of the subjects reported that the images which they conjured up were of unusual vividness, were usually characterized by bright colours, and had considerable detail. All these subjects were unanimous in their opinion that their images were more vivid than anything they had previously experienced. Several subjects who normally had great difficulty visualizing scenes could now visualize them almost instantly with great vividness.… One subject … could visualize faces of former associates of a few years back with almost picture-like clarity, a thing which he was never able to do previously. This phenomenon usually appeared during the second or third day and, in general, became more pronounced with time.

Such visual heightenings — whether due to disease, deprivation, or drugs — can take the form of enhanced visual imagery or hallucination or both.

In the early 1960s, sensory deprivation tanks were designed to intensify the effect of isolation by floating the body in a darkened tank of warm water, which removed not only any sense of bodily contact with the environment but also the proprioceptive sense 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 scientific 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 effects 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 first hours of blindfolding, but always by the second day, whether their eyes were open or not.