A face-recognition experiment needs an answer the subject can give clearly. Archerfish supplied one with a behavior already perfected for another job: they spit focused water jets at targets above the surface. Researchers displayed two human faces and trained a fish to fire at the chosen image, turning a splash into a recorded decision.

The first experiment grew to 44 faces. The learned target had to be selected against many unfamiliar alternatives, not merely one repeated opponent. In the second, researchers controlled color, brightness, and the outline of the head so those broad cues could not carry the answer. The fish still discriminated among 18 faces.

That ability bears on a larger argument about brains. Human face recognition is often associated with specialized processing, and birds that recognize faces possess brain structures sometimes compared functionally with a neocortex. Archerfish do not bring the same anatomy or a domesticated history of living among human faces. Yet they learned the image problem to high accuracy.

The correct claim remains specific. These fish were trained in a two-choice laboratory task, rewarded for choosing a target picture. They did not recognize friends, infer identities, or demonstrate a natural interest in human portraits. What they showed was powerful pattern discrimination: general visual systems in a fish could learn distinctions that human observers experience as faces. Their water jet made that hidden computation visible one precise spit at a time.