Refuted
Goldfish have a memory span of only three seconds.
A piece of folk wisdom holds that goldfish forget everything within three seconds, making them effectively immune to boredom in their bowls.
The evidence
Multiple controlled studies, including work at Plymouth University and the Technion in Israel, have shown that goldfish can remember trained associations for at least several months. Fish have been taught to push levers for food at specific times of day and to navigate mazes.
The "three second" figure has no scientific basis and appears to be folklore.