Fish may not have a three-second memory after all. A new study has found that archerfish, a tropical aquatic creature, can distinguish between human faces and retain the memory over a long period of time.
The new study
Several studies in 2015 found that certain kinds of fish have the capability of recognising members of their own species. The new study by scientists of the University of Oxford (UK) and University of Queensland (Australia) for the first time shows that fish have powers of human facial recognition too. The scientists chose archerfish for the study because it is known to shoot out jets of water to target aerial insects, at times three metres above the water surface. The scientists used this quality of the fish to train them to recognise human faces. After their training, the archerfish, known to have powerful eyesight, spat water at a familiar face and continued to do so in repeated experiments.
The scientists used four archerfish for the experiment. Each of them were placed in an aquarium one-by-one and a digital screen was placed next to it. The fish were individually trained to recognise the faces.
For this, the scientists began with showing the fish a set of two human faces. Initially the fish randomly spit jets of water in all directions. But whenever they threw water in the direction of the face the scientists wanted them to, the fish was rewarded with food pellets. Over time — ranging between a few days to two weeks in some cases — the archerfish began to remember the faces.
To test the training, scientists then displayed 44 faces on the screen and the archerfish managed to throw water at the right face 81 per cent of the time. Then the scientists decided to standardise the heads in all the faces and even then the fish spotted the right face 86 per cent of the time.
An intelligent creature
Human beings and other primates are known to have the powers of facial recognition because of a large and complex brain. Fusiform gyrus present in the neocortex area of the brain is responsible for facial recognition in humans and animals such as dogs, horses and some birds. The fusiform gyrus is said to be linked to various neural pathways that helps human beings remember faces.
But in case of fish, which has a much smaller brain, neocortex and hence the fusiform gyrus doesn’t exist at all. It is based on this that scientists have for long argued that fish cannot feel pain or recognise faces. Remember the forgetful Dory in Disney’s Finding Nemo? But now, research such as this credit fish with much more intelligence.
Some scientists say fish possess certain brain circuits that allow for “sophisticated discrimination” between external objects. These circuits, they say, enable them to identify food, predators, and mates. Several fish species are capable of learning complex spatial relationships and forming cognitive maps to memorise the area they are inhabiting.
In the latest study, scientists have said that the fish were not looking at the human face as a whole; instead, their brain was trying to “look for patterns” and store them in their memory. That is how they managed to remember the faces. However, what remains unclear is which part of the brain is responsible for storing these memories.
Scientists now plan to carry out the experiment on other species of fish and see if they get a similar response. Understanding visual distinction in fish will also throw some light on the human brain function. Scientists now want to examine whether facial recognition in humans in innate or acquired.