You've almost certainly heard the so-called fact that a goldfish's memory lasts only three seconds, but that's a fish tale.
It's surprisingly simple to prove that goldfish have relatively good recall; just try what Australian teenager Rory Stokes did in 2008. Stokes taught his goldfish to connect feeding with a red Lego block he would drop in the tank. After a few weeks, he removed the block. Then, a week later, he put it back, and the goldfish swam right to it, obviously expecting a meal. Other experiments have suggested even longer memory spans, as demonstrated when goldfish learned to associate feeding with the sound of a bell, then came towards that sound after not hearing it for six months.
Research has also shown that goldfish can tell one person from another, recognize the person who feeds them, and grow less afraid of someone they see frequently. They've even been taught to navigate mazes and push balls into nets. In other words, goldfish clearly have a lot more going on than we give them credit for.
- In captivity, a goldfish can live for 40 years or more, although a lifespan of 10-15 years, with proper care, is more common.
- Although they typically stay small when kept in a small aquarium, goldfish can grow to a foot (.3 m) in length when kept in a larger enclosure.
- Goldfish sleep with their eyes open – they have no choice, since they have no eyelids.