Fish and Mirrors: a Major Flaw in Aggression Studies

A recent study of fish and their reflections has revealed that they are not as gullible as researchers have long thought, potentially undermining the results of many past studies of aggression.

For decades mirrors have been used to trigger aggressive responses in territorial and less self-aware species such as birds or fish. Now, however, a study has revealed that many fish species may have not been reacting to their reflections in the same way as they would react to a rival fish.

The study, just published in the journal Animal Behavior, details how convict cichlid fish (Amatitlania nigrofasciata) were found to react slightly different when facing a true rival, compared to when they were forced to face their refection in a mirror.

The study specifically found that convict cichlid fish tend to swim next to one another in a head-to-tail configuration when looking for a fight. When facing a mirror this simply cannot happen, as the fish will find that it will just keep bumping into the perceived mirror "rival" every time it tries to move forward.

The researchers theorized that if the agitated fish truly did want to pick a fight with its reflection, it would start moving side to side in an attempt to "fake out" the alleged competitor. But if the fish quickly realizes the true nature of the reflection, the "aggressive reaction" researchers think they are seeing may in fact be an unusual example of fishy vanity.

Study author Robert Elwood, an animal behavior researcher at Queen's University in Belfast, UK told Nature News that he likes to compare this kind of behavior to boxers.

If a fish is truly looking for a fight with its reflection, it will move quickly and "stay on its toes." However, "if it's just posturing in front of a mirror, a 'boxer' can stand around and pose for ages," he said.

Russell Fernald, at Stanford University in California, added that he thinks the trouble is "that scientists generally underestimate the cognitive skills of fish."

Fernald published a study in the journal Biology letters back in 2010 that details how the cichlid fish actually boasts different neural activity when facing an "antagonistic" mirror compared to an actual rival, indicating that the fish knows there is something different going on.

"We have shown that cichlid fish can do logical reasoning. Fish can infer social rank by observation alone. So why should they be fooled by a mirror?"