It is popularly held that gold fish are only able to remember very short spans of time. Even though the myth was debunked years ago, many still believe that the low-maintenance pets have three-second long memories.
"I mean it never really seemed feasible to me, that they had a three, five, 10 second memory because animals need their memory, so they build up over time a knowledge of where the food is," said Stokes. "It seemed pretty impractical for a species to evolve without these capabilities."
He conducted the experiment as a class-room assignment. In his experiment, he fed the fish next to a red lego. "At first they were a bit scared of it, a bit wary,” said Stokes, “but by the end of the three weeks, they were actually almost coming before I put the food in.” Stokes then removed the lego and fed the fish normally for a week before reintroducing it to the aquarium.
"They remembered perfectly well," he said.
Dr. Culum Brown of Sydney's Macquarie University, who has studied fish for more than ten years, praised the youngster's work. "The thing that I really liked about Rory's experiment is he not only got that classical conditioning going [but] the fact that he could get them respond just to that specific coloured marker I thought was really good," he said. Brown had conducted studies of fish native to Australia. He said the fish he studied were able to escape a net in five trials, and still retained the information a year later.
Other researchers have trained goldfish to play fetch, do the limbo, and respond to different lighting and sounds. In one experiment, researchers put a button in the tank that would dispense food if pressed at a certain time of day. The goldfish eventually learned to push the button during this time and left it alone the rest of the day. In another, goldfish which were taught to associate a sound with feeding time, were released into the ocean and returned to the spot where they were released when the tone was played on a loud speaker six months later. Discovery Channel's celebrated series “Myth Busters” also conducted a 'mini myth' experiment which proved goldfish were able to remember how to navigate a maze to obtain food.
Many believe that the myth of the goldfish's short memory was essentially a marketing ploy to sell pets and aquariums. Keeping a creature in a confined space for the duration of its life seems cruel unless it's constantly forgetting where it is.
Brown advised fish owners, “I think the more complicated you make your fish tank, the happier your fish is gonna be. In fact, the best thing to do is to keep changing it around, so make it interesting for them.You'll find that if you do that, your goldfish will be much more active and much happier in general."