The ultimate horror in science fiction is neither death nor destruction but dehumanization, a state in which emotional life is suspended, in which the individual is deprived of individual feelings, free will, and moral judgement. That the most successful SF films of the past decade seem to be concerned with dehumanization simply underlines the fact that this type of fiction hits the most exposed nerves of contemporary society: collective anxieties about the loss if individual identity, subliminal mind-bending, or downright scientific/political brainwashing. (Not by accident the trend began to manifest itself after the Korean War and the well-publicized reports coming out of it of brainwashing techniques.)
We have come a long way from Metropolis and the encroachment of the machine. Nowadays man can become the machine himself. The automatoned slaves of modern times look perfectly efficient in their new painless state. From this aspect, they are like the zombies of old-- only we never bother to wonder if zombies were happy in their trance.
--Carlos Clarens: An Illustrated History Of Horror and Science Fiction Films (1895-1967). New York: Putnam, 1967.