 Swarm theory observed in non-human societies is a related concept and is being explored as it occurs in human society.Scottish journalist Charles Mackay identifies multiple facets of herd behaviour in his 1841 work, Extraordinary Popular Delusions and the Madness of Crowds.Currency crises tend to display herding behavior when foreign and domestic investors convert a government's currency into physical assets (like gold) or foreign currencies when they realize the government is unable to repay its debts.