Investor herding

Herd behavior describes how individuals in a group can act collectively without centralized direction. The term can refer to the behavior of animals in herds, packs, bird flocks, fish schools and so on, as well as the behavior of humans in demonstrations, riots and general strikes, sporting events, religious gatherings, episodes of mob violence and everyday decision-making, judgement and opinion-forming.

Raafat, Chater and Frith proposed an integrated approach to herding, describing two key issues, the mechanisms of transmission of thoughts or behavior between individuals and the patterns of connections between them. They suggested that bringing together diverse theoretical approaches of herding behavior illuminates the applicability of the concept to many domains, ranging from cognitive neuroscience to economics.

A group of animals fleeing from a predator shows the nature of herd behavior. In 1971, in the oft cited article "Geometry For The Selfish Herd," evolutionary biologist W. D. Hamilton asserted that each individual group member reduces the danger to itself by moving as close as possible to the center of the fleeing group. Thus the herd appears as a unit in moving together, but its function emerges from the uncoordinated behavior of self-serving individuals.

Asymmetric aggregation of animals under panic conditions has been observed in many species, including humans, mice, and ants. Theoretical models have demonstrated symmetry-breaking similar to observations in empirical studies. For example, when panicked individuals are confined to a room with two equal and equidistant exits, a majority will favor one exit while the minority will favor the other.

Possible mechanisms for this behavior include Hamilton’s selfish herd theory, neighbor copying, or the byproduct of communication by social animals or runaway positive feedback.

Characteristics of escape panic include:

The philosophers Søren Kierkegaard and Friedrich Nietzsche were among the first to criticize what they referred to as "the crowd" (Kierkegaard) and "herd morality" and the "herd instinct" (Nietzsche) in human society. Modern psychological and economic research has identified herd behavior in humans to explain the phenomena of large numbers of people acting in the same way at the same time. The British surgeon Wilfred Trotter popularized the "herd behavior" phrase in his book, Instincts of the Herd in Peace and War (1914). In The Theory of the Leisure Class, Thorstein Veblen explained economic behavior in terms of social influences such as "emulation," where some members of a group mimic other members of higher status. In "The Metropolis and Mental Life" (1903), early sociologist George Simmel referred to the "impulse to sociability in man", and sought to describe "the forms of association by which a mere sum of separate individuals are made into a 'society' ". Other social scientists explored behaviors related to herding, such as Freud (crowd psychology), Carl Jung (collective unconscious), and Gustave Le Bon (the popular mind). Swarm theory observed in non-human societies is a related concept and is being explored as it occurs in human society.

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