Jan. 24, 2007 — It appears that some fish are surprisingly good at figuring out their place in the pecking order, according to new research. So good, in fact, that they may possess a certain reasoning capability that even humans don't show until age four.
In an experiment, male cichlid fish (Astatotilapia burtoni) were allowed to watch five of their vigorously territorial brethren challenge each other from the safety of a separate small aquarium. In the staged battles, fish 1 beats fish 2, which beats fish 3, and so on to fish 5, the last loser.
To guarantee the outcome of each battle, the researchers deliberately tired the intended losing fish before the confrontation by holding them out of the water, which basically makes them out of breath.
"Then (the winning fish) just pummels him," said Logan Grosenick, a student at Stanford University in California and lead author of a paper on the experiment in the Jan. 25 issue of the journal Nature.
The researchers then placed the "observer" fish between two of the fish that had participated in the battles. In nearly every insatnce, the observer fish swam away from the fish it judged as the more formidable adversary — the one with more battle victories.
To make that decision, the observer fish may have used a kind of reasoning known as "transitive inference."
This is, basically, the ability to judge who's the stronger adversary based on where the other fish fall in a hierarchy the observer fish must piece together in its head.
