Pedestrian crowds can form the substrate of important socially contagious behaviors including propagation of visual attention, violence, opinions and emotional state. However, relating individual to collective behavior is often difficult, and quantitative studies have largely employed laboratory experimentation. In the only previous study of gaze-following in human crowds, Stanley Milgram et al. (1969) instructed stimulus groups to stop and stare up into a building window on a crowded street in New York City, measuring the probability of passersby adopting this behavior. Although informative to the effects of social influence in public settings, these findings raise several interesting questions. What is the strength of this contagion response? What are the functional reasons pedestrians follow the gaze direction of others? Can cues provided by the visual attention of others provide valuable information regarding the location and identification of pertinent, but weak or ambiguous, stimuli? To what degree this is response context dependent?

OPEN ACCESS – See the full study by clicking HERE.

We performed two studies in which we used semi-automated analysis to track the motion and head direction of 3,325 pedestrians in natural crowds (see picture on the right and video below), quantifying the extent, influence and context-dependence of socially transmitted visual attention. In our first study we instructed stimulus groups of confederates within a crowd to gaze upwards towards a single point atop of a building. Analysis of passersby demonstrates that the probability of pedestrians adopting this behavior increases as a function of stimulus group size, before saturating for larger groups. This response has important consequences for how information about environmental stimuli is acquired socially between pedestrians. Many group-living animals use quorums (i.e., k>1) in response to the presence or behavior of others, allowing them to make consensus decisions in which all (or the majority of) individuals adopt the same choice. Conversely, the proportional-saturating response established here did not generate strong consensus. We developed a model that predicts this gaze response will lead to the transfer of visual attention between crowd members, but is not sufficiently strong to produce a “tipping-point” or “critical mass” of gaze-following that has previously been predicted for crowd dynamics.

This first experiment also showed that visual attention spreads unevenly in space. Individuals with trajectories leading them to walk behind the visual orientation of the stimulus group exhibited a higher propensity to follow the gaze of the stimulus group. This suggests that gaze-following under these conditions is not due to social pressure or some form of obedience. Instead, individuals followed gaze direction more often when the person they were copying could not observe their behavior. A similar rearwards transfer of visual attention has also recently been observed in bi-directional pedestrian traffic (Gallup et al., in press), suggesting that within natural settings gaze-following is strongly mediated by social interaction and facilitates acquisition of environmentally relevant information.

A second experiment, in which passersby were presented with two male confederates performing suspicious/irregular activity, supports the predictions of our model. Although pedestrians appeared to follow each other’s gazes towards the stimulus, and this was particularly the case for the suspicious-acting condition, there was no tipping point at which large numbers of individuals simultaneously gazed in that direction. Overall, visual interactions between pedestrians occurred primarily within a 2-meter range. This localized response, and the propagation of copying mainly by those not under observation of others, further reduces its the efficiency for transferring information about the location of weak signals or subtle features of the environment.

Click here to view the embedded video.

To explore the context dependence in this response, these experiments were performed in two urban settings – a busy shopping street and a bustling city train station. In the thoroughfare pedestrian gaze was drawn towards the suspicious actors at close distances, while in the train station gaze was drawn towards nearby control activity but averted from those exhibiting suspicious activity at very close positions. We hypothesize that aversion in a crowded commuter station consisting of largely stationary individuals could be because close proximity and directed gaze communicate threat or dominance. Further analyses indicated that male pedestrians accounted for this close range gaze-avoidance.

While the above aspects of gaze-following response are reproduced robustly between experimental setups, the overall tendency to respond to a stimulus is dependent on spatial features, social context and the sex of the passerby. In summary, this approach has produced quantitative and qualitative insights about a candidate causal link in the relation between individual and crowd behavior: the propagation of attention.

PRESS COVERAGE:

1. What are you looking at? People follow each other’s gazes, but without a tipping point (Discover Magazine)

BIBLIOGRAPHY:

1. Gallup, A.C., Hale, J.J., Garnier, S., Sumpter, D.J.T., Kacelnik, A., Krebs, J. & Couzin, I.D. (2012) Visual attention and the acquisition of information in human crowds. PNAS, published online April 23rd, open access.
2. Milgram, S., Bickman, L. & Berkowitz, L. (1969) Note on the drawing power of crowds of different size. Journal of Personality and Social Psychology 13, 79–82.
3. Gallup, A.C., Chong, A. & Couzin, I.D. (2012) The directional flow of visual information transfer between pedestrians. Biology Letters, published online March 28th.

Please note that these commentaries may contain views, or interpretation, not shared by the authors. We strongly encourage those interested to read the original paper – which can be downloaded for free from our publications page.

The first section of the supplement is also accessible for those wanting to know some more about the modeling and experimental protocols used. 

- As is emphasized in our title, this study is related to democratic consensus decision-making in animal groups such as schooling fish, flocking birds, herding ungulates etc. (this is not to be confused with democratic societies).

- We are not studying human voting systems in this paper, although the reader may note that we do demonstrate how group-living animals can effectively 'vote' without explicit ability to count etc.

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America votes with the fishes

Jeffrey Kluger, TIME

The Tea Party and the Occupy Wall Streeters owe a lot to a little fish called the golden shiner. Golden shiners are not very high on the aquatic food chain. They measure just 3 to 5 in. (7.5 to 12.5 cm) and serve as so tasty a finger food for bigger, more aggressive species that humans use them as bait fish. But the golden shiner can have strong opinions — deeply, fiercely held ones. And that, according to an improbable new study published in the journal Science, can tell us a lot about how American democracy works.

Read more: http://www.time.com/time/health/article/0,8599,2102612,00.html#ixzz1hGgQFrmF

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Vote for apathy?

Rob Waugh, The Daily Mail

 But a new Princeton study suggests that the opposite could be the case – and that people who have no interest at all could be vital to the working of a democratic society. The uninformed are essential to democracy because their apathy helps to dilute the effect of powerful minority interests – for instance, highly educated elites – who would otherwise dominate public life. A well-informed, interested public is often hailed as the 'ideal' of democracy.
Read more: http://www.dailymail.co.uk/sciencetech/article-2076026/The-uninformed-essential-working-democracy-study-finds.html#ixzz1hGfkN7PQ

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How ignorance could improve group decisions

Kate Shaw, Wired, 2011-12-16

How do groups of animals make collective decisions? Last week, we learned that bees reach consensus by headbutting those with opposing views. But in many other species, the decision-making process is a bit more democratic. In cases where social animals are unrelated and have different self-interests (such as our own), contrasting opinions are common. But it can be just as common for individuals to either be uninformed about the options, or simply not care much about the decision.

(more) 

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Disinterested 'key in democracy'

BBC.co.uk, 2011-12-16

Disinterested individuals are vital for achieving a democratic consensus, according to a study in the journal Science.

(more) 

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Why a democracy needs uninformed people

Emily Badger, Miller-McCune, 2011-12-15

In a lesson taught by schools of fish, researchers determine that uninformed individuals are actually a benefit to democracy by sanding off extreme views.

(more) 

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Uncommitted newbies can foil forceful few

Susan Milius, ScienceNews, 2011-12-15

Decisions can be more democratic when individuals with no preset preference join a group

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Study of fish suggests the value of uninformed voters

Paul Basken, The Cronicle of higher education, 2011-12-15

As Congress proves itself increasingly dysfunctional and captive to extremists, lots of people may be asking themselves: What kind of fish-brained voters keep electing these guys?

(more) 

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Minnows reveal power of the 'uninformed'

AFP, ABC Science, 2011-12-15

It might sound fishy, but US researchers say minnows make perfect lab rats when it comes to exploring the surprising power of the uninformed in group decision-making.

(more) 

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Less Knowledge, More Power: Uninformed Can Be Vital to Democracy, Study Finds

Science Daily, 2011-12-15

Contrary to the ideal of a completely engaged electorate, individuals who have the least interest in a specific outcome can actually be vital to achieving a democratic consensus.

(more) 

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Ist Ignoranz wichtig für die Demokratie?

Eva Obermüller, ORF.at, 2011-12-15

Der mündige und informierte Bürger ist Grundlage jeder funktionierenden Demokratie, so die gängige Annahme. Eine Studie besagt hingegen: Unwissende, interesselose Individuen sind ebenso wichtig für den demokratischen Konsens.

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Democracy may depend on the ignorant

Joseph Castro, LiveScience, 2011-12-15

Ignorance can be bliss, but it seems it can also promote democracy.

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Can ignorance make a better democracy? In fish it can…

Joseph Castro, MSNBC.com, 2011-12-15

Minority can persuade majority, until the unknowing come along, study finds.

(more) 

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A democracy depends on uninformed individuals, maybe

Improbable Research, 2011-12-15

A democracy without a substantial number of uninformed individuals, may not know what it’s doing, metaphorically speaking. So implies this new study

(more) 

PopTech is a yearly conference that focuses on tech and social change, and a global community of innovators, working together to expand the edge of change.

How useful would it be to find a cure for autism? Energy sources less likely to contribute to climate change? Disaster early warning systems based on sound waves? Ways to enable remote surgery or speed up stroke rehabilitation?

PopTech is proud to introduce a dynamic group of people who are working toward those goals and more: the Science and Public Leadership Fellows Class of 2011. From analyzing malaria to crowdsourcing basic science, this year’s Fellows are spearheading research that has the potential to change the world. We’re bringing them together this week at National Geographic headquarters in Washington, DC, with a faculty of experts who will help them further develop the leadership, collaboration and communication skills to become more effective leaders within the scientific community and amongst the general public at large.

Wheeling, turning, and diving—flocks of birds and schools of fish perform these acrobatic maneuvers with the precision of fighter jets in formation. Hundreds, sometimes thousands, of individuals coordinate their movements in a whirl of motion. Some collectives are so cohesive, people used to think group members employed telepathy to communicate changes of shape or direction.

But as Princeton University biologist Iain Couzin has discovered, the mysterious motivations of animals engaged in collective behaviors are anything but supernatural.

Couzin has found that only a small percentage of a group of animals, like fish or humans, can dictate the movements of the entire group. Couzin’s human studies showed that the placement of "informed leaders"—people who know where they’re going—near the center and periphery of groups increased the speed and accuracy with which the group moved towards a target. His latest work, on the role of uninformed followers, will soon be in press.

Couzin also has shown that different species form groups using similar principles. Perhaps best known for his work on locust swarms, Couzin uses innovative approaches to study collective animal motion—earning him the 2008 Searle Scholar award for outstanding research by a young investigator. Popular Science included him in its annual Brilliant 10 list for 2010.

At the February 2011 American Association for the Advancement of Science meeting in Washington, D.C., Couzin broke from a herd of journalists and researchers to speak with SciCom’s Jane Lee about collective animal motion—and how video games help him do his job.

You can find the complete article at this address: http://www.economist.com/node/18226831

In The New Yorker, Iain's work is described in John Seabrook's essay "When large crowds assemble, is there a way to keep them safe?", about the events at the Wal-Mart in Valley Stream, Long Island, on Black Friday, 2008, that led to the death of one of the store's employees, Jdimytai Damour. Iain is cited in this essay as an expert of crowd dynamics, along with Pr. Dirk Helbing and Pr. Jens Krause. 

In its post "The mathematics of fish schools and flocks of humans" on Ars Technica, Matt Ford summarizes the recent symposium "Mathematics and Collective Behavior" that held on Friday, February 18, during the annual AAAS meeting in Washington. 

Postdoctoral Research Associate

In this article, Sepideh presents experimental and model data linking the nutritional state of locusts with their mass migration behavior. The article can be found here. Hereafter is its abstract:

In order to move effectively in unpredictable or heterogeneous environments animals must make appropriate decisions in response to internal and external cues. Identifying the link between these components remains a challenge for movement ecology and is important in understanding the mechanisms driving both individual and collective motion. One accessible way of examining how internal state influences an individual's motion is to consider the nutritional state of an animal. Our experimental results reveal that nutritional state exerts a relatively minor influence on the motion of isolated individuals, but large group-level differences emerge from diet affecting inter-individual interactions. This supports the idea that mass movement in locusts may be driven by cannibalism. To estimate how these findings are likely to impact collective migration of locust hopper bands, we create an experimentally parametrized model of locust interactions and motion. Our model supports our hypothesis that nutrient-dependent social interactions can lead to the collective motion seen in our experiments and predicts a transition in the mean speed and the degree of coordination of bands with increasing insect density. Furthermore, increasing the interaction strength (representing greater protein deprivation) dramatically reduces the critical density at which this transition occurs, demonstrating that individuals' nutritional state could have a major impact on large-scale migration.