Flocks of birds and schools of fish are two common examples of collective motion. Though herding behavior in animals is well recognized, humans exhibit their own set of emergent phenomena. For example, pedestrians walking down the sidewalk form lanes, and stadium crowds perform "The Wave". In more extreme situations, like those found during an earthquake or a fire, panicked crowds can stampede causing injury and even death. Thus, scientists try to figure out how to build buildings (or stadiums, concert halls, etc.) to mitigate these risks. However, it's not exactly ethical to start a riot for the sake of science, so we're limited to simulating evacuations either with volunteers or on computers. The problem with this is that panicked humans act according to very different social rules, adding a element of uncertainty to this research. To address this concern, we used the extreme social conditions found at heavy metal concerts as a proxy to explore the emergent behaviors humans can exhibit in atypical circumstances. To get an idea of what happens, see the YouTube videos at the bottom of this page. These pictures also illustrate the basic situation:
Before (Photo credit: Ulrike Biets)
After (Photo credit: Ulrike Biets)
Evidently, heavy metal concerts are distinctly different from ordinary pedestrian traffic...
In this work, we analyzed videos posted on YouTube.com that were recorded at heavy metal concerts. Using automated tracking techniques to quantify the crowd's motion, we examined the statistical character of mosh pits, a collective phenomenon where the participants (moshers) move randomly, colliding with one another in an undirected fashion. Much to our surprise, we found this collective motion quantitatively resembles classical 2D gasses. To try and understand the reasons why, we used a flocking-based simulation to investigate the phenomenon. Flocking simulations model living beings as simple particles, reducing complex behavioral dynamics to a few basic rules. In our case, we used two populations of simulated moshers, which we dub Mobile Active Simulated Humanoids, or MASHers. Active MASHers move around and have a tendency to follow their neighbors (in the technical literature, this is called "flocking"), while passive MASHers prefer to remain stationary. Mixing active and passive MASHers together, we found that when random collisions dominate the tendency to flock, the statistics of mosh pits are quantitatively reproduced. On the other hand, when the situation was reversed and flocking dominated randomness, we found an ordered vortex-like state. Looking back at videos of metal concerts, we found that actual moshers exhibited this vortex-like phenomenon too. These so-called "circle pits" spontaneously emerge from the simulation and are an interesting example of collective behavior in humans.
These results have important implications for the study of human crowd behavior during escape panic, protests, and riots, suggesting that certain types of collective motion are only accessible in genuinely excited states. Thus, the emergent phenomena commonly occurring at heavy metal concerts present new avenues for reliably, consistently, and ethically studying human collective motion in extreme conditions.
The following videos give examples of some of the collective behaviors studied in this project.
FAIR WARNING: There is some profanity in the videos below.
(Related note: co-author Jesse Silverberg was at the concert shown in the movie above)
An example mosh pit from our simulation:
An example circle pit from our simulation:
- Read the full article published in Physical Review Letters here, or the short-form version on the arXiv here.
- Try an interactive version of our simulation here.
- NPR's Morning Edition aired an interview and "Research News" piece on the physics of mosh pits, which can be listened to here.
- Reuters TV produced a piece for mass distribution to television news channels. Watch the video here or on Scientific American here.
- Scientific American did podcast about the physics of mosh pit available here.
- Listen to radio interviews with co-author Jesse Silverberg on CBC's As It Happens here, WHCU's Morning News Watch here, and read the transcript from WTOP's interview here. Jesse was also interviewed on the radio programs You Study WHAT?? produced by Australian Public radio (2/25/13), Coast Breakfast with Bern Young (3/4/13), and Afternoons With Glynn Greensmith (3/7/13).
- Watch co-author Matt Bierbaum deliver a talk about mosh pits at the 2013 APS March Meeting here. Matt was also interviewed on Madrid's La Hora del Metal by Lisveth Hernández (3/3/13) and can be heard here. The program was rebroadcasted in El Salvador on Metal Critico (3/3/13). Matt was also interviewed on Germany's DRadio Wissen (3/5/13) and can be heard here.
- Jesse, Matt, and Itai Cohen were interviewed on WVBR's The Sunday Forum with Tommy Bruce (3/10/13). Jesse and Matt were interviewed for the Physics Buzz Podcast at APS March Meeting 2013 and can be heard here (see related blog post here).
- Our project was featured on the Discovery Channel's show Daily Planet (2/14/13), as well as The Prime Show, on Japan's WOWOW channel (3/5/13). See the segment here.
- A very interesting analysis of tweets about the mosh pit paper by Altmetric can be found here.
- SourceFed did a blurb about the physics of mosh pits that can be viewed here. It's really funny too!
Follow the press coverage:
NBC, National Geographic, Popular Science, Popular Science (again), New Scientist, Physics World, The Times, The Atlantic, The Chicago Reader, Smithsonian, The Huffington Post (written by co-author J.L.S.), The Telegraph, ABC Science, MIT Technology Review - arXiv Blog, Improbable Research, The Register, Phys.org, Physics Central, Physics Central Buzz Blog, Inside Science, Guitar World, Revolver, Spin, The Verge, Gizmodo, Examiner, DR, Yahoo! News, Hacker News, io9, Line Out @ The Stranger, Nerdcore @ Crackajack, Alt Press, News.com, AUX.tv, Metafilter, Slashdot, Motherboard, Txchnologist, The Creators Project, The Kevin Houston Blog, Synchronized Minds (Tommi Himberg Blog), Alan Cross Blog, CBC Music, Break Through Radio, Global Domination, NME, Metalsucks, Metal Injection, Metal Hammer, Animal, GSA, Thrash MTL, Tone Deaf, Ultimate Guitar, No Clean Singing, A Metal State of Mind, Braingell Radio, Blabbermouth, Jam Spreader, At Most Fear Entertainment, Loudwire, ToDaMax, Thrash Hits,Top News, Konbini, Sounds, Tert, NWT online, Lenta, Tempo, Hypothesis, Nerd D3, XFM, Unsigned Expenditures, Chaos Cartel, Musica Diabolus, Topix News, Ca Muz, iPon, Atlantico, Brooklyn Vegan, GMA news, Dangerous Minds, KROQ, Neatorama, TEOTI, The Wild Children, Videosift, Geekapolis, Syracuse, Rock NYC, Wish You Would Hear, Antimusic, Dailymail, Gaffa, Knovel, Planet Ivy, Skruff, Q103, Up the Downstair, The Sound and the Fury, Dying Scene, Pedestrian TV, HLN, Ligonier Living, Pages Digital, Pheonix New Times, Line Logic, Alligator, Cay Compass, Homeland Voice, Current, ZME Science, No Country For New Nashville, APA340, Live Fix, Capital Gazette, C&EN, Open Culture, The Dish, The Ithaca Journal, Reddit (Various threads in Physics, Science, Science (again), Metal, Ska), Cornell Alumni Magazine, Cornell Chronicle, Cornell Daily Sun, and Cornell Physics.
Cornell grad student Kathryn McGill produces a YouTube Vlog called the Physics Factor that highlights the fun and interesting world of physics. She recently interviewed Matt and Jesse about their work on mosh pits -- everyone had a lot of fun and the vlog can be viewed below. Be sure to check out the blooper reel for some behind-the-scenes action!
Note: Field work was independently funded by J. L. Silverberg.