Last Tuesday’s episode of Horizon, called Total Isolation, is available for viewing and download at the BBC iPlayer website for the next 2 days. In the 50-minute documentary, Professor Ian Robbins, a trauma psychologist at the University of Surrey who specializes in supporting torture victims, reconstructs a highly controversial study first performed in the 1950s.
The new study involved six subjects who volunteered to experience 48 hours of complete sensory deprivation. The volunteers first performed a battery of tests designed to assess various cognitive functions, such as visual memory, verbal fluency and suggestibility. They were then deprived of all sensory stimuli for 2 days, and observed throughout, before performing the same tests again.
It is well known, from numerous animal experiments, that sensory stimuli are essential for proper brain development to occur. However, there are very few studies of the effects of sensory deprivation on humans, largely because of the highly unethical nature of the experiments involved.
The original study was led by the preeminent psychologist Donald Hebb (1904-1985). It was funded by the U.S. military, in order to determine the effects on American and Canadian prisoners held under such conditions during the Korean War, but was quickly aborted because it was considered to be cruel.
The Horizon episode includes footage of Hebb discussing the results of the original study, and expressing his surprise at the dramatic effects of even short periods of sensory deprivation. These effects can be seen clearly in the volunteers involved in the reconstruction. They become anxious very quickly, and some of them experience visual and auditory hallucinations.
From the animal work, it is clear that such deprivation leads to weakening of the synapses within the brain’ s sensory systems. This almost certainly occurs in humans too – as the second set of tests shows, the volunteers’ general ability to process information was significantly reduced.
These effects are, of course, reversible, as the volunteers were deprived of stimulation for just 48 hours. But the findings have obvious implications for the tens of thouseands of prisoners around the world who are held under such conditions for much longer periods of time – this could lead not just to weakening of synapses, but to large-scale loss of connections throughtout the brain.
The volunteers in the new study were also found to be more suggestible after than before the sensory deprivation, which raises serious doubts about the reliability of information obtained from prisoners who have been kept in solitary confinement. Robbins discusses all these issues in the programme, and this article in The Times contains more information.