Panic, Irrationality, and Herding: Three Ambiguous Terms in Crowd Dynamics Research

Table 8

Review summary of the empirical studies on herding.

Ref.	Aspect of behaviour			Experiment method				Evidence of herding		Further details
	Exit (direction) choice	Exit (direction) choice changing	Reaction time	Human crowds	Virtual reality	Ants	Mice	Observed	Not observed
[62]	•					•		•		Herding observed in the form of asymmetric use of exits by ‘panicked’ ants
[59]	•					•		•		The degree of asymmetry increased linearly with the temperature
[60]	•					•		•		The degree of asymmetry increased then decreased by ants’ density
[61]	•					•		•		Ants under stress demonstrated the phenomenon of ‘‘symmetry breaking’’.
[42]	•			•		•			•	Symmetry breaking was associated with the difference in the width of exit in proportional ways
[140]	•						•	•		The mice exhibited herding behaviour while escaping from a pool of water in a two-exit flooded chamber
[92]	•						•	•		The mouse experiments yielded lower throughputs caused by herding. Herding prevented the full utilization of the two exits.
[91]	•						•	•		The occurrence of blind copying is suggested by the uneven (biased) utilization of the available; pool space and exits by untrained members especially in the larger 30-mouse groups
[52]	•				•				•	Experiments in interactive virtual-reality setting ruled out the herding effect
[54]	•				•			•		[In a non-crowded virtual tunnel evacuation], participants under social influence treatment were more likely to follow the virtual agent
[55]	•		•		•			•		(i) [In a non-crowded virtual tunnel evacuation], Participants were less likely to move to the emergency exit in the conflict conditions; compared to the no-conflict condition.; (ii) The presence of passive virtual agent made subjects delay their movement reaction
[56]	•				•			•		(i) [In a non-crowded virtual tunnel evacuation], exit choice is jointly influenced by both exit familiarity and by the egress behaviour of neighbours.; (ii) Social influence increases with the number of neighbours
[50]	•				•			•		Occurrences of herding behaviour are affected by both environmental and personal factors.
[47]	•				•				•	People prefer searching for an exit and avoiding smoke rather than following the crowd
[40]	•				•			•		The observed herding patterns do not result from a change in the herding tendency but instead from the crowdedness
[58]			•		•			•		(i) The more people someone sees leaving, the; more inclined this person is to leave.; (ii) Seeing people leave has more impact than seeing people stay.
[64]			•	•				•		(i) Social influence is an important factor in reaction time especially when fire cue is unclear; (ii) Social influence (on reaction time) increases with decreasing distance between visitors.
[48]	•			•					•	Social influence (on exit choice) is moderated by the level of decision ambiguity
[45]	•			•					•	(i) Social influence (on exit choice) does not necessarily increases with decreasing distance between individuals.; (ii) [In a crowded evacuation], exit choice is jointly influenced by both social interactions and physical factors; (iii) Social influence increases with the number of neighbours
[53]	•			•					•	(i) Social influence is moderated by the effect of individual differences; (ii) Social influence (on exit choice) does not necessarily act to the direction of herding
[41]	•			•					•	(i) Social influence acts to the opposite of herding; (ii) Stress does not increase imitation tendency; (iii) The number of neighbours moderate the social influence
[49]	•			•					•	Mis-specifying herding tendency can substantially bias modelling outcomes
[65]	•	•		•				•	•	(i) Individuals show clear imitative tendency in changing their exit choice decisions; (ii) Individuals do not show herding tendency in their exit choices; (iii) Herding tendency of individuals (in exit choice) does not increase by stress
[66]	•	•		•				•	•	(i) Social groups show clear imitative tendency in changing their exit choice decisions; (ii) Social groups do not show herding tendency in their exit choices; (iii) Herding tendency of groups (in exit choice) does not increase by stress