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When someone forgets something almost immediately, they’re often told they have the "memory of a goldfish"—a phrase meant as an insult rather than a compliment. This image of the goldfish as a creature of fleeting memory, however, is a misconception that persists worldwide.
Dr. Culum Brown, often called the "champion of fish intelligence," has pointed out that the myth appears in many cultures, each attributing different time spans to a fish’s memory, but the underlying stereotype remains the same: fish are perceived as forgetful and unintelligent.
Recent research contradicts this narrative. Goldfish are routinely selected for cognitive studies precisely because of their unexpectedly robust memory and learning capabilities. Experiments have shown that they can recall cues and rewards for hours, days, and even weeks, with some evidence suggesting retention over years.
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Goldfish possess both short‑term and long‑term memory. Short‑term memory allows them to navigate immediate tasks, such as following a food trail, while long‑term memory helps them remember past experiences that could be crucial for survival.
In a 2014 study published in Proceedings of the Royal Society B, researchers at Oxford taught goldfish to swim specific distances in response to visual cues. Even after the cues were removed, the fish reliably returned to the starting point, expecting a reward. This demonstrates that goldfish can retain spatial information tied to reinforcement.
Long‑term memory is evident in everyday observations of pet goldfish: many can anticipate feeding time and remember which side of the tank food is released. More sophisticated experiments have trained goldfish to press paddles that dispense food, and the fish continued to favor those paddles days after training concluded. Other studies have shown goldfish retaining maze layouts for several months, and even recognizing conspecifics after prolonged separation.
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Goldfish are not the sole exemplars of fish memory. Over the past six decades, a growing body of evidence has highlighted the cognitive abilities of numerous fish species.
In Canada, researchers published in Frontiers in Behavioral Neuroscience that African cichlids returned to the exact spot in their tank where food had been dispensed 12 days earlier, even after being relocated to a different enclosure for that period.
A 2016 study from the University of Padova in Italy examined Poecilia reticulata (guppies) in maze trials. With each successive trial, individuals navigated the maze faster and made fewer mistakes, indicating both spatial memory and learning from trial and error.
Swiss scientists in 2019 investigated the cleaner fish Labroides dimidiatus. After being captured and released back into the wild, half of the fish hid upon sight of nets 11 months later—a clear indication that they remembered the negative experience.
