Fish know to stop the spread of misinformation

Many social animals rely on each other for survival – for example, alerting one another when danger is present.

But what happens when there is a false alarm?

False alarms are the most common kind of misinformation among wild animals. An example of this is when an individual in a group produces an alarm signal or makes a run for it when no real danger is present.

Such actions in an individual can be perceived by others in the group as an indication of threat. It can result in a cascade of escape responses spreading erroneously.

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Previous studies have shown how behavioural responses in an individual help control flawed decision making in such scenarios. But it hasn’t been clear until now how groups of animals control their exposure to misinformation.

A new study of foraging fish takes this question up and shows that such misinformation is quickly stopped from spreading.

Researchers on French Polynesian reefs placed cameras to record the behaviour of wild foraging fish of different species.

The scientists analysed the footage, comparing it to reconstructions of the sensory information available to the fish before, during and after escape events. They then modelled the fish’s decision-making process to assess whether the animal responded or not.

Camera observatory in a coral reef in French Polynesia shows a “false alarm”. Credit: Florida Atlantic University.

No more than a few individual foraging fish usually took the misinformation bait according to the results, despite escape events occurring frequently in the absence of predators. The researchers found that the animals form dynamic information networks of visual cues between each other.

“These networks are surprisingly robust to false alarms that occur when one individual flees in the absence of a true shared threat,” says Ashkaan Fahimipour, an assistant professor at Florida Atlantic University. “By reconstructing visual sensory inputs to each animal, we show that this robustness to misinformation about threats inherits from a specific property of their decision-making strategy: dynamic adjustments in sensitivity to socially acquired information. This property can be achieved through a simple and biologically widespread decision-making circuit.”

Escape responses in fish are controlled by specialised neural circuits that process sensory stimuli before passing the information on to premotor neurons in the brain. These neurons, also called “mirror neurons” are active when the individual is performing an action, or when observing another individual performing that same activity.

It’s thought, then, that escape responses are triggered by visual cues produced when individuals in the group move.

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The study’s results match up with previous thinking that animals pool the behavioural cues from neighbours to make decisions. The fish were able to dynamically adjust their response given the information available from others nearby.

“It will be interesting to investigate whether the mechanisms revealed here also are important in driving individual decision-making and misinformation spread in other biological and social systems,” Fahimipour adds.

The study is published in the Proceedings of the National Academy of Sciences journal.

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