When it comes to counting, fish do swimmingly, according to a new study that describes the first published evidence of such behavior.
Captive mosquitofish—a North and Central American freshwater fish named for its taste for mosquito larvae—successfully counted geometric shapes in recent laboratory experiments.
Ten of the naturally social fish were first trained inside their tank to associate a door permitting them to move into different compartments and join their larger group with a certain number of shapes.
The same fish were then tested several times in an otherwise empty, unfamiliar tank to see whether they would choose to swim through the door marked with the right number of shapes.
: a psychological condition or a relationship in which a person is controlled or manipulated by another who is affected with a pathological condition (as an addiction to alcohol or heroin) ; broadly : dependence on the needs of or control by another