Facing Facts About Fish Brains

By Ralph Birch

There’s something fishy going on Down Under.

A recent study conducted by scientists from the University of Oxford and Australia’s University of Queensland has concluded that a species of tropical fish possesses the ability to recognize faces. Despite the lack of a neocortex, which is the part of the brain that controls visual recognition, the archerfish has demonstrated the ability to accurately distinguish between faces more than three-quarters of the time.

The archerfish, which is native to Australia and southeast Asia, was selected for this research based on its ability to spit a jet of water. This technique is typically utilized as a defense mechanism against insects looking to prey on the archerfish, but scientists used the spitting as a way for the fish to choose between faces.

Researchers presented the archerfish with two different images and offered food as a reward when a particular face was selected.

“This can give us a huge amount of information about what the fish is able to see and how they do it,” said Dr. Cait Newport of the University of Oxford, who has also performed similar experiments with Picasso triggerfish.

In subsequent tests, the archerfish viewed a series of learned faces and was able to distinguish between those images and up to 44 new faces with an 81 percent success rate. The fish were able to identify the faces even when features like head shape and color were removed from the images.

The Australian study found that complicated brain makeup is not necessary to recognize human faces, though the identification of subtle features is a key component. Newport and her colleagues now believe that fish have significantly greater visual discrimination abilities than previously believed.

Heading Home

This level of cognition shown by fish could relate closely to the ability of certain species to return to the same territory, year after year, for breeding. Fish look for unique colors, patterns and textures to find their breeding grounds — but mass bleaching of coral reefs could make this more difficult.

Bleaching of reefs occurs when water is too warm, which forces coral to expel living algae. The algae calcify and turn white and eventually die, which is a threat to locations like the Great Barrier Reef and the marine life native to that region.

“We don’t know if they’re still going to be able to find their territories, their homes,” Newport observed. “We don’t know how that will affect how they detect predators or potential prey.”

Fishy Business

The archerfish aren’t the only fish that display amazing brainpower. Researchers were able to train grey bamboo sharks to recognize and remember shapes. They remembered their training for at least a year.

Damselfish can see UV patterns on other fish and can detect the lack of lines in similar species. This helps them distinguish between fish that belong to their species and fish that don’t.

If there is one lesson to learn from this fascinating research, it’s don’t underestimate fish.