DANGEROUS MOBS VS. WISE CROWDSdays on end until they dropped down dead. Another famous example is
the fits that afflicted girls during the Salem Witch Trials of the seven-
teenth century. A local doctor was unable to explain the fits experienced
by two girls who’d been experimenting with fortune telling, and so he
blamed the supernatural, claiming the girls had been “bewitched”. Soon
other girls and young women were experiencing the same fits, as hysteria
spread through the community. A more recent manifestation was the
emergence of “railway spine” in Britain in the nineteenth century –
passengers reported feeling faint and suffering back pain. Experts at
the time blamed the effect of 30mph speeds on the body, but in fact the
symptoms were purely psychological.
The catalyst for mass hysteria is often prolonged stress, and the mani-
festation is usually influenced by the beliefs of the day. For example, in
the case of the dancing plague in Strasbourg, the local population had
endured months of famine, and they had a long-held belief in the power
of saints and devils to unleash dancing curses.
Outbreaks of mass hysteria still occur to this day, often in schools,
where the presence of large groups of people in relatively confined areas
provides a fertile breeding-ground for a psychological contagion to spread,
especially during stressful periods like exam time. In a typical case in 2007,
for example, staff at a specialist science-college in South Yorkshire feared
a gas leak when over thirty pupils and a teaching assistant suddenly fell
ill. It all started when three children complained of feeling queasy during
a class screening of a biology video. As more and more children reported
similar symptoms, the emergency services were called and the school was
abandoned. However, no gas leak or other environmental cause was found,
and of the 32 pupils taken to hospital, all were discharged after four hours.
The wisdom of the crowd
Before closing this chapter, let’s take a brief digression away from tyranny
and conformity to look at one of the clearest and most intriguing exam-
ples of the positive side of group psychology – a phenomenon known
as “the wisdom of the crowd”. This is the finding that if you average the
verdict of a group of people, their combined estimate will be more accu-
rate than even the most expert individual. Francis Galton found this out
in 1906 at the West of England Fat Stock and Poultry exhibition, when he
averaged the estimates made by 787 people in a competition to guess the
weight of an ox. The group’s averaged guess was 1,197 pounds, just one
pound below the ox’s actual weight. Moreover, the crowd’s joint estimate