Andrew's recent spate of Bradbury reading has reminded me of how often characters in his 1950s stories bring up "mass hysteria/neurosis/delusion/psychosis" as the go-to explanation for whatever weird thing is happening. Of course, these characters always turn out to be wrongity-wrong-wrong, but it makes me wonder how strong the belief was, in mid-century America, that groups of unrelated individuals could just all suddenly experience the same form of mental illness at once.
Current descriptions of "mass hysteria" generally focus on cases where a group all fall ill and no physical cause can subsequently be discovered; and even so many people point out that this explanation can't be positively proven, it's just what's left if investigators can't find any other explanation. Mass hallucinations or delusions sound a much less plausible phenomenon; is this is some popular-but-discredited theory of the time? a fictionalized version of cold-war paranoia/McCarthyism (cough cough The Crucible cough cough)? or an idea sparked by the 1951 mass psychosis of the French village of Pont-St-Esprit (which did happen, and was blamed at the time on ergot, but
may have been a CIA experiment)? Googling "mass hallucinations", "mass hysteria" "mass psychosis" + "1950s psychology" turns up very little.
Is it all related to the idea of brainwashing, as in The Manchurian Candidate (1962)? Brainwashing seems to held the same place in the imagination of the 1950s and 1960s that hypnosis did to folks in the 19th century, and that weird electric helmets strapped to peoples' heads did in 1940s movie-serials. When The Manchurian Candidate was remade in 2004 the mind control is accomplished by the latest sinister SFnal gadget, nanotechnology. The original Korean-war cases of "brainwashing" seem to have recanted not long after being rescued, and today sound more like "prisoners playing along so their captors won't kill them" than people actually having their beliefs altered.
Basically sanity and social coherence are fragile but I'm curious as to how often, if ever, they break in this particular way.