Many people say that a goldfish can remember things for only three seconds. But this is not true. In experiments, goldfish learned the way through a maze, a kind of puzzle with many paths.

They also learned a rule with a light and still remembered it a few days later. If you keep goldfish, you may see them swim to the top when you come near. They may remember you and their food time!

A common joke says that goldfish forget everything after three seconds. But no study has ever shown this, and experiments point the other way. In 1999, Spanish researchers trained goldfish on two spatial tasks.

The fish learned where the food was by using landmarks. They could also use the whole space around them like a map. A later study found that part of the goldfish brain seems to work like the hippocampus, the memory center in mammals.

Why did the three-second story spread? Perhaps it made keeping fish in small tanks seem acceptable. Goldfish can remember for much longer than that. In the 1960s, American scientists taught goldfish to swim to the other side of a tank after a light signal, and the fish still remembered the rule days later.

In a series of experiments, López and colleagues placed goldfish in a cross-shaped maze with food hidden in one arm. The fish could find it in two different ways. They could follow a single cue, or they could form something like a mental map of the surrounding space, a flexibility once thought typical of rats and birds.

When the team later damaged one region of the goldfish forebrain, place learning was selectively impaired, so that region seems to play a role similar to the hippocampus in mammals. Older work on retention tells the same story. In classic avoidance experiments from the 1960s, goldfish learned to respond to a light signal and still showed the learned behavior when retested days later. Against this background, the famous three-second memory looks like pure folklore.

No experiment has ever produced that figure. Memory span is not a single number anyway, since it depends on the task and on how long researchers wait before testing. A 2015 review argued that fish cognition rivals that of many other vertebrates. How we think about fish minds has practical consequences. If people believe a goldfish forgets its surroundings in seconds, poor living conditions can seem perfectly acceptable.