Mass hysteria, per Wikipedia’s definition, is “a phenomenon that transmits collective delusions of threats, whether real or imaginary, through a population in society as a result of rumors and fear.” You may be familiar with famous incidents of mass hysteria such as the Dancing Plague of 1518 or the Salem witch trials, but you likely haven’t heard of a much more mundane yet relatably close-to-home instance: the Seattle windshield pitting epidemic of 1954. Considered by experts to be a “textbook” case of collective delusion, residents of Bellingham, Seattle, and other communities of Washington reached a state of panic when they began noticing “holes, pits, and dings” in their windshields.
[O]riginally thought to be the work of vandals[,] the rate of pitting was so great that residents began to attribute it to everything from sand flea eggs to nuclear bomb testing.
Originating in Bellingham in March, police initially believed the work to be vandals using BB guns. However the pitting was soon observed in the nearby towns of Sedro Woolley and Mount Vernon and by mid-April, appeared to have spread to the town of Anacortes on Fidalgo Island.
Within a week, the news and the so-called “pitting epidemic” had reached metropolitan Seattle. As the newspapers began to feature the story, more and more reports of pitting were called in. Motorists began stopping police cars to report damage and car lots and parking garages reported particularly severe attacks. […] By April 15, close to 3,000 windshields had been reported as affected.
Finally, Sergeant Max Allison of the Seattle police crime laboratory stated that the pitting reports consisted of “5 per cent hoodlum-ism, and 95 per cent public hysteria.” By April 17, the pitting suddenly stopped.
While troubled motorists propounded a number of theories to explain the pitting, ranging from “cosmic rays” to a shift in the earth’s magnetic field, the likeliest explanation is that “natural windshield pitting had been going on for some time, but it was only when the media called public attention to it that people actually looked at their windshields and saw damage they had never noticed before.”