Crabs and crowds

Over the past week, many news outlets have reported on the discovery of four crab species in the freshwater rivers in the Palawan province. According to the paper by a German researcher affiliated with De La Salle University announcing the discovery of these crabs, despite the close-up photos of various crab anatomies, none of the new species are longer than an index finger. The paper, which appeared in the Raffles Journal of Zoology back in February, is also notable for burying what is perhaps the most striking feature of these new species till the very end: the bright red or purple hues of the crab shells.

One of the theories about the crabs’ colors is that they play a role in how the crustaceans socialize, though more studies need to be done to resolve this question.

Researchers studying human behavior also place a lot of importance on how visuals can influence social relationships, and this was the topic of a recent publication by an international team from the United Kingdom, the United States and Sweden.

“Among social organisms, the ability to perceive and interpret the behavior of others can be critical to survival, whether it provides clues to foraging sites or an alert to an immediate predation risk,” noted the team led by Princeton behavioral researcher Iain Couzin in their paper. With this in mind, the team focused on how crowds react when a group of people in their midst start watching the same thing.

Similar experiments have been done before, but under more controlled conditions. For this study, Couzin and his colleagues took advantage of current technologies to track what every person in the crowd was looking at in order to answer their questions.

In one experiment, actors were sent out to a busy street in the United Kingdom either by themselves or in groups of up to 15 people and instructed to look up at a video camera. In reviewing the video afterward, researchers took note of how many passersby responded to the group action by looking up and how many people ignored the event and just kept going.

Crowd behavior

Anyone who’s been caught in traffic jams as lanes of motorists slow down to take in an accident on the other side of the road before speeding on will likely predict that if a group of people starts watching something, chances are good that others in the crowd will follow suit. Consider online videos of flash mobs in amusement parks or public transportation hubs that show passersby taking notice of what’s going on over time and pausing to watch the full spectacle.

In comparison to the above examples, the team particularly chose to do something designed to be less obvious, and they found that the crowd response was accordingly weaker. The results were neither unanimous nor from the majority of the passersby, but it was proportional to the size of the starting group of actors. While the researchers did not get all of the pedestrians to look up, if they had more actors looking up in the first place, then a larger percentage of the passersby were more likely to copy their movements.

“Although pedestrians seemed to follow each other’s gazes to the stimulus,” the researchers reported in their conclusions, “there was no tipping point at which large numbers of individuals simultaneously gazed in that direction.” They added that their results suggest that studying crowd behavior by itself is not enough to really understand how social behaviors are affected or influenced by the visual cues being presented by others.

The study was published ahead online the week of April 23 in the Proceedings of the National Academy of Science USA.

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