You Asked
Do goldfish have only a 10 second memory? — Sonia, Sydney, Australia

Marshall Answered
The idea that goldfish have a really short memory has been around for a long time, but was made mainstream by the movie named “Goldfish Memory” (the first 50 seconds of this video lays out the premise of the movie):

So, is it true that goldfish have no memory? It turns out it isn’t, and it was proven by a student in Australia in 2008:

Schoolboy explodes goldfish memory myth

He did a typical Pavlovian conditioning experiment, using a blinking light and food. After several weeks, the fish understood that when they saw the blinking light, food would appear. So whenever the light blinked, the fish would rush toward it. He then removed the light for a week. When he put the light back in, the fish retained their memory of it and immediately rushed toward it. Therefore, goldfish can remember certain things for a week or more, just like most creatures with brains.