Another interesting source on crowd dynamics

I’m finally realising the usefulness of twitter and in the most unlikeliest of ways. I’d been follwoing cracked.com mostly for the jokes and then they tweeted this earlier today:

http://www.cracked.com/article_19004_6-things-that-annoy-you-every-day-explained-by-science.html

And that had some references to annoying things in crowds and some actual references to work being done in crowd dynamics. That too the exact kind of work I was looking for. And I’ve stumbled on a few new papers and research. Shall post the updates soon. But here are the first interesting page I found: http://mehdimoussaid.com/project4.html . Just posting so that i don’t forget.

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A rough summary of what I’ve read in behavior models

Aveni1977 : “the extent of anonymity variablein crowds should be treated as a variable rather than a constant”  =>  crowd comes as both individulas and groups. but more gourps can be formed during the emergency or the event. Also behavior of groups and unassociated individuals need to be studied

individually.

 

Some of my thoughts :

A mechanism is needed wherein the groupng tendency among individuals in the simulation increases with time and the extent of the danger.

Also individuals in groups and isolated behave differettly

The question is how does this increase in grouping come about? Do individuals group with every other individual?

zeleny1981 : If the choices are very similar more information is sought from the environment to make decision.

 

Stahl1982 : One of the first papers to use a computer simulation to model fire evacuation and justified the use of simulations for fire safety studies.

 

Sime1983 : Introduced the concept of affiliative behavior :the identity of an individual’s primary group and the groups proximity and availability determine the reaction of a user to the primary group. degree if threat(ambiguity of cues) is also important

Paulsen1984 :

When alone, 75 percent of the subjects reported the smoke. In the presence of two nonreacting others (confederates of the experimenters} only 10 percent of the subjects reported the smoke during the experimental period. : Latane and Darley [40]       

Sime1985 :

Engineering = too much emphasis on environment too little on behavior

psychology = too much on behavior too little on environment

 

Tong&Canter1985: Talks about factors that influence reaction to fire:

intensity and spread of smoke, previous experience of fire, training, and direct threat perception

 

In early stage, there is uncertainity….”This uncertainty results from the ambiguous nature of the information available so that fire victims consistently become involved in investigative and exploratory actions to deter- mine the nature of the threat they are facing.””The cues which most commonly motivated an initial inquiry by building occupants were strange noises, unaccustomed behaviour of others, such as running, and occasionally there was a direct

encounter with smoke or flames. ”

 

‘feedback in action’ (p. 119), which suggests that people are continuously acting in re- sponse to new information rather than being motivated from an inert condition.

 

individuals display an ‘autonomous capacity to be interested in the environment‘.

 

There is a tendency for people to first dress, because they expect to encounter others, then to investigate, and finally, to return to their rooms.

 

 

Sandberg1997 : reiterates importance of pre movement time and inefficiency of usual fire alarms.

Much of the movement in the early stages of fires is characterised by activities such as investigation and not escape.

Individuals often move towards and with group or family members and maintain proximity as far as possible with individuals to whom they have emotional ties.

People’s ability to move towards exits may vary considerably

 

Observed behaviour in fires:• People’s behaviour in fire depends on the roles that they perceive to be relevant to their responsibility.

• People prefer to use familiar routes for escape.

• People do not always react in their best interest.

 

The activities undertaken during the response time include /12/:

• investigate what has happened, i.e. seek further information (Determine the source, reality or importance of fire alarm)

• help others (seeking and gathering companions) • save material property (money, other risks) • try to fight the fire • call the fire brigade • leave the building

• ignore the danger • the time involved in other activities not fully contributing to effective evacuation

 

Characteristics of agents that influence their evacuation times:

1. Alertness

2. Mobility

3. Social Affiliation

4. Role

5. Position (standing or lying down.. )

6. commitment

7. Focal POint

8. Familiarity

9. Communications

 

 

 

Gwyne et al, 1999 : Excellent taxonomy and comparison of existing models.

According to this paper there are 5 kinds of models:

1. no behavior

2. Funcational analogy: use an equation or set of equatio0ns to the entire populations: not defined individually… and no meaning as such, just seems similar to the meaning we expect it to have. movement predicted from equations might not even be calibrated

3.Implicit  models: behavior implicitly represested tyhrough complex physical models. Problem is that they’re based on secondary data which incorporates psychological and sociological influences. The data might be wrong

4.Rule based systesm: with explicit rules.

5. AI-based.

 

Graham2000 : Loss aversion’s manifestation in evacuation::avoid action for small problems;drastic action as things go out of control.Early action might result in huge losses so people wait till later to do anything decisive

 

Fahy et al2001 : Lots of data on evacuation speeds, pre movement times, etc. etc.

 

Ozel2001: contains theory on decision making in fire emergency

“This also represents the basic premiseof this study , whic states that given the semae set of information, people may atttend to information differently depending on the degree of stress and the amount of time pressure they experience, “sic.

 

decision making is episodic and there are between and within episode decision making taking place.  Some of these decisions tend to overlap. while execution,i.e., they’re still thinking what to do about hte next episode, etc.

 

Acceleration, avoidance of decision and filtration help to reduce time pressure useful when threat of negative outcome > threat of incomplete info.

Bolstering : better at least in one and equal in all others.

4 different phases of decision making:

unconflicted inertia                 :credibility of initial source of information(fire alarm, etc.) is assesed.

unconflicted change                 : recognise and start getting more emionaly aroused

defensive avoidance                 : THis is the most likely stage of strategy choice and uses increased filtering, pesimism, accelerated processing of informatino bolstering, etc. Also more likely to follow others. affiliation plays a key role

hypervigilance                        : Panic is extreme case of hypervigilance, bad decision making coz of bad info processing.

cue utilization decreases with increasing pressure

 

The useres prefer less risky choicse as time goes by and stress increases… so they are more likely to take familar exits as time progresses and stress and time pressure increases

 

Exits with negative associations are generally not taken when stress increases. because these are prohibited during non emergency situations

 

 

Proulx2001: Some things taht are reiterated:

About panic :  People do get scared… but according to psychologists panic refers to irrational behavior and as such ppl alwys behave rationally depending on their beliefs at the tmie.

Besides, experience, age, mobility, leadership skill, etc. one key factor is the role of the individual in that setting… for eg. a chef in restaurant vs owner vs client.

visitors and guests expdct to be taken care of.

Steps in evacuation:

First be sure of fire..

next find children, pets or valuables

then evacuate

Also contains some stats on pre evac time

 

 

Reicher2002 : Has a good discussion about the history and older theories of crowd behavior and his proposed new (and generally well accepted) theory of crowds.

 

Emergent Norm theory ( Turner and Killian) : Before crowd action takes place there is characteristically an extended period of ‘milling’ during which people engage with others, proffering their own accounts of reality and listening to that of others. leader then develops and unanimity results

SCT : social categorisation theory : many selfs.. identity with a category, follow group consensus.. leaders can impose there will….

 

Personal identity defines how I, as an individual, am unique compared to other individuals while social identity defines how we, as members of one social category are unique compared to members of other social categories (Turner, 1991, 1999;Turner, Hogg, Oakes, Reicher & Wetherell, 1987).

On defining ourselves as category members we participate in a process of self stereotyping. That is, we seek to determine the relevance of category identity for action in context and we conform accordingly. We expect fellow group members to do likewise and therefore we also expect to agree with them on matters pertaining to our mutual social identity. Being part of a psychological crowd (as opposed to a set of people who simply happen to be co- present) does not entail a loss of identity but a shift to the relevant social identity.

 

ESIM: An elaborated social identity model for crowds                                                                                                                                                                                     Groups formed are highly dependent on context and other groups and in turn individuals present.so a group formed is not static, it has a dynamic characteristics. behavior ina group reaches a common level with time and adversity. ESIM regards social identity as a model of self in social relations, along with the actions that are proper and possible given such a social position.

it can be seen how acting on identity leads to a change of identity due to the dynamics that ensue from a mismatch between how certain crowd members saw their social location and how the police (re)located them.

 

Isobe etal2003 : (Helbing group), Nagaietal2004 : Experiments on effect of smoke and visibility limitations in escape behavior.

This is done by blindfolding ppl and observing exit behavior. Herding was observed.

The problem i feel is that these eperiments assume visibility is always 0 … but in an actual scenario it gradually decreases… so for high level exit choice, I don’t think smoke is that important since that decision would generally already have been made… but at lower level it might be hte key

 

Cornwell2003 : . Aguirre, Wenger, and Vigo (1998) argue that people who belong to larger groups take longer to evacuate because it takes them longer to orga- nize

bond strengths also exist… some weaker bonds can break as the emergency progresses.

Hypothesis 1: Fatality risk will be relatively high among those with no primary ties, relatively low among those with few primary ties (where the benefits of cooperation are theoretically maximized), and increasingly high as primary group size increases.

Hypothesis 2: Individuals for whom at least one primary group member died experienced greater fatality risk.

Hypothesis 3: The effect of a primary group member (or primary group members)dying on the fatality risk of another group member is partially due to the strength of the bond(s) between (among) them.

 

 

Cocking&Drury2005 :

Individual panic does occur but rather than the panic spreading through the crowd it is the calm people who mange to impose their will on other ppl and calm the people who get worked up.

 

 

Mawson2005 :

The typical response to threat is neither flight nor fight.. its actually a search for affiliation. Greater need for affiliation than avoiding physical danger.

Talks mostly about how affiliations is generally just as important or sometime more important than escape.

 

Interesting point :  fligth behavior can be explained as moving from certain situation to other situations that are perceived as familiar. (not objectively safest position)

 

 

Cocking&Drury2007 : Basically establish experimentally three hypotheses:

1. Panic does not happen

2. Orderly altruistic and coooperative behavior almost always happens except when the crowd rush makes such helpful behavior impossible.

3. This helpful behavior because of a shared common identity created in response to the shared threat faced.

 

 

 

 

Proulx2007 : Mostly reiterates her old ideas :

initial inertia.. its only when ambiguos cues accumulate or are suppplemented by additional cues that ppl actually start investigating. Engage in “milling”

pre movemetn time and may include movement but not movement towards escape. Fire fighting is also part of pre movement time( role in society) :In real emergency evacuations, a wide variety of times have been reported: from 5 minutes to over 25 minutes.

Familiarity of routes, trainging and presence of fire wardens or helpers and what others are doing are what influences route choice in fires.

 

SchadSchneider2008 :

Panic does not occur.

Herding as a terminology is very vaguely defined hence it is better to avoid the terminology altogether

Collective effects that should be there in a model crowds:

  • jamming
  • Density waves ( at 7 persons per square meter shockwates are felt that propel ppl at least 3m)
  • lane formation
  • Oscillations : in counterflow at bottlenecks .
  • patterns at intersections : maybe roundabouts or something like that

 

velocity always decreases with increasing density.

 

reiterates social attachment theory.

 

A comprehensive theory of pedestrian dynamics has to take into account three different levels of behaviour (Fig. 8). At the strategic level, pedestrians decide which activities they like to perform and the order of these activities. With the choices made at the strategic level, the tactical level concerns the short-term decisions made by the pedestrians, e.g. choosing the precise route taking into account obstacles, density of pedestrians etc. Finally, the operational level describes the actual walking behaviour of pedestrians, e.g. their immediate decisions necessary to avoid collisions etc.

 

Cocking&Drury2008 :

UNIty and group identity in the crowd icnreases with time because of a common psychological cause.

NO MASS PANIC : individual instance of panic was there. But no mass panic.

more help to existing groups, might help others. Stick to societal roles.

Everyday norms are upheld and queues are formed.

 

 

Drury et al2008 :

” Thus, we would argue that the social identity approachto mass emergency evacuation we have tested and found support for in the studies reported here takes us be- yond previous advances in the field in certain impor- tant ways. Although the normative approach (e.g., John- son, 1987a, 1987b) clearly transcends the mass panic model by pointing to the predominance of sociality even within life-threatening mass emergency crowds, it col- lapses back into the mass panic model when it claims that competitive behavior increases at times of greatest urgency (Johnson et al., 1994; cf. Quarantelli, 1957). The normative approach follows the affiliation model in emphasizing the role of preexisting interpersonal re- lationships in limiting panic (e.g., Cornwell, 2003; Fein- berg & Johnson, 2001; Johnson et al., 1994). But the affiliation model too collapses back into the assumptions of the mass panic approach when it suggests that panic can occur when there are no familiar figures or features present (Mawson, 2005). What is missing from all these models is an explanation for the evidence of positive af- fective, motivational, and behavioral relations to a crowd of strangers in an emergency evacuation. By contrast, SCT suggests that the shift from personal collective identity leads us to define others’ interests in line with our own, instead of understanding them as counterposed. In such contexts, one might even help strangers at a risk to the personal self.”

 

Kobes2010 : Brilliant short compilation of existing work on fire evacuation