It's enough to make this writer seriously consider vegetarianism: A new study has found that fish can recognise human faces.
The paper, published in Scientific Reports, found that archerfish—a tropical species that can shoot water jets from its mouth—could learn to distinguish an image of an individual human's face from others, even when the pictures were controlled for colour and head shape.
Lead author Cait Newport said that the motivation of the work was to better understand how humans recognise faces. She explained that there are two theories on how human facial recognition works: One suggests that this skill relies on complex and specialised brain circuitry such as that in the human neocortex; the other suggests that it's a learned skill that doesn't necessarily need this brain structure.
"We wanted to disentangle these two ideas and see if we could use another species to figure out if we do in fact need really specialised cells, or if maybe something else that doesn't have these specialised cells can learn this task," Newport said. "That's why we turned to fish, because they have no evolutionary need to recognise human faces, and they lack this entire section of the brain—the neocortex."
The researchers showed their four fish two faces on a monitor over their aquarium and taught them to spit at one but not the other for a food reward. Then, they showed the fish 44 other faces alongside the one they'd been taught not to spit at (as the fish apparently form a stronger association with negative stimuli). The fish could discriminate the face they knew with an average accuracy of 81 percent.
The fish could even distinguish the face when all of the images were controlled for head shape, colour, and brightness (though Newport noted that the faces were always shown in 2D, frontal views).
The results suggest that you don't need a neocortex to recognise human faces, even if our brain structures are particularly designed to be good at this.
Newport said she was surprised at how good the fish were, but noted that previous research has shown at least some species of fish can tell each other apart by the intricate patterns on their face. Asked how the fish compared to humans, she said she'd actually attempted to compare them.
"I actually did try to do a small pilot study with PhD students," she said. "Three of them did really well and one of them got only about 70 percent accuracy, but I'm not sure what he was doing," she said. Perhaps, like the fish, it can take a little training to get your eye in.
The research has implications for understanding how the brain works and could also potentially inform computer facial recognition.
"It suggests this task isn't necessarily as difficult, or there may be simpler ways that it can be achieved," Newport said. "That's really interesting and it [raises] the question as to why the human system is so complicated if a really simple system can do it."
To the important question: Does this mean that a pet fish could recognise its owner's face?
"Potentially," said Newport. She pointed out that their work was with archerfish, not goldfish, and that there's a lot more to the task when a fish sees you walking toward it (it could respond to markers like movement or height rather than facial features).
But if nothing else, the research offers more evidence against the common assumption that fish are somehow dumb (the myth that they have a three-second memory has been rebutted over and over).
"I think it's really fascinating that they have these supposedly simple brains in terms of the actual structure of it, but they're still able to use them for really complicated tasks, and we probably just don't give them enough credit," Newport said.