Goldfish Do Not Have a Three-Second Memory

Few animals have been as unfairly insulted as the goldfish. It is the standard example of a short memory. People say that a goldfish forgets everything within three seconds, so every lap of its bowl is a brand-new adventure and every little plastic castle a thrilling surprise. It is a charming idea, and it turns up in jokes, films and conversations everywhere. It is also completely wrong. Goldfish can remember things for months.

According to BBC Wildlife's Discover Wildlife, goldfish can retain memories for at least three months, can be trained and can even tell the time. Researchers at the University of Mainz in Germany, who trained goldfish with food rewards, describe them as telling colours apart with great precision. With a little patience and a reward of food, goldfish can be trained to respond to coloured light signals and even to perform simple tricks.

The time-telling part is the most delightful. In experiments at Plymouth University in England, goldfish learned to push a lever to release food. Then the researchers changed the rules so the lever only worked for one hour each day. The fish did not keep pressing all day long in hope. They learned when the lever worked and nudged it at the right time. Many goldfish owners notice something similar at home, because fish fed at about the same time every day learn to expect dinner.

Goldfish also learn who their people are. Their eyesight is good enough to tell individual humans apart, and many owners notice that their fish rush to the front of the tank or up to the surface when they approach, while hiding from strangers. Over weeks, and sometimes months, a goldfish that sees people regularly stops treating them as a threat, and it can become possible to feed it by hand.

Their senses are remarkable too. Goldfish have four types of colour-sensing cone cells in their eyes, including one sensitive to ultraviolet light, which means they may see a range of colours that humans cannot. They also have one of the most studied senses of hearing among fish. An animal equipped like that has every reason to pay attention to its surroundings, and a three-second memory would be a strange partner for such good senses.

The goldfish also has a long history with people, which makes the insult even less fair. Goldfish come from carp that were raised in China, where a colour mutation was noticed centuries ago and fish were selectively bred for their gold and red colouring more than a thousand years ago. Even today, young goldfish are often a metallic brown, like their wild ancestors, and can take up to a year to develop their familiar colours.

So how do we know the three-second story is a myth? Because it can be tested, and it has been, again and again. Fish that remember a lever, a feeding time or the face of their owner are showing learning that lasts far longer than a few seconds. Nobody is quite sure where the myth began. But the next time someone calls you a goldfish for forgetting something, you can reply that goldfish would probably have remembered.