Be careful who you call "fishbrain." The insult might actually be a compliment, based on a new study in Scientific Reports. For the first time, scientists have discovered that a species of fish can distinguish between human faces—something once thought possible only among primates with large, complex brains. To see if simple brains without a neocortex were capable of the feat, researchers trained archerfish—tropical freshwater fish that spit water from their mouths—to spit water at a human face displayed on a computer monitor positioned near their tank. Researchers then flashed the face on the screen along with 44 others, reports Motherboard. In 81% of cases, the fish spit water at the face they'd previously been shown. When the faces were of a standard color or head shape, the rate improved to 86%, per CNN.
"The fish continued to spit at the face they had been trained to recognize, proving that they were capable of telling the two apart," study co-author Cait Newport of Oxford says in a release. Distinguishing between human faces is no easy task since "human faces share the same basic features," Newport explains. The study notes fish probably haven't evolved the ability for human facial recognition over time because of limited contact with humans. But the study suggests that at least some fish have "sophisticated visual recognition capabilities," per the release. "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," Newport says, adding it's possible that pet fish recognize their owners. "We probably just don't give them enough credit." (A study finds plastic is making fish stupid.)