Humans aren't the only ones who tend to squeeze when they're in a hurry, achieving the opposite effect and slowing their progress. Studies have shown that sheep, for example, do the same. Recently, researchers from France examined this behavior in another animal that moves very differently: fish. They discovered that, unlike humans and sheep, the fish took turns and avoided pushing and blocking the passage. They did this by keeping their distance from each other to a minimum, even when they felt threatened.
The researchers examined neon tetra fish (Paracheirodon innesi), small freshwater fish, about three centimeters long, that live in South American rivers and are common as aquarium fish. They put 30 fish in an aquarium that was divided into two sections, with a small opening between them. At first all the fish were in one section, and then one of the researchers took a small aquarium net and with its help "grazed" the fish towards the opening, until they all moved to the second section.
Tetra fish, photo: Getty Images
Social rules
The researchers were able to control the size of the opening, changing it from 1.5 centimeters in diameter to four centimeters in diameter. Not surprisingly, the fish took longer to pass through the opening the smaller it was. What did surprise the researchers was the fact that the fish were not pushed and blocked the passage. They huddled near the opening, but kept their distance from each other and did not push each other, even as the net approached them and pushed them into the partition.
"We interpret this behaviour as respecting social rules, even in emergencies," Orly Dupont and Filipe Peyla, two of the co-authors of the paper, told BBC Science Focus. "Humans, as well as sheep, seem to quickly forget social rules when faced with a stressful situation, and adopt selfish behavior."
Go to the fish, robot
In nature, of course, fish do not need to pass through a small opening between two parts of an aquarium. But they often live in shallow water, and have to make their way between stones and rocks. Since they are sociable fish that move in large groups, and are small fish that many larger fish see as prey, it is likely that neon tetrafish occasionally encounter a situation in which several dozen fish have to quickly exit through a narrow passage. That's probably where their ability to take turns and keep their distance from each other developed. Similar behavior has been observed earlier in ants, which also go out in an orderly manner and do not block passage, even when they are in danger.
It would be too much to expect people to learn from neon tetra and, based on their example, stop squeezing and blocking each other in narrow passages. But there are others who can: robots. Some types of robots move in coordinated groups, and rules such as those obeyed by fish, such as the distance of one individual from another, may be very suitable for them. Another type of robot, autonomous cars, will also be able to adopt a behavior model based on the behavior of fish, especially in a situation where there are many autonomous cars on the road that need to regulate their movement. At least in the case of robots they are less likely to panic and forget the rules, as we tend to do.
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