Goldfish remember for months, not seconds

The idea that a goldfish has a three-second memory is a myth. Goldfish can remember things for months. Even the myth cannot agree with itself: depending on where you hear it, the supposed memory lasts anywhere from about two seconds to ten, but it is always short.

The most direct evidence comes from a study at the University of Göttingen in Germany, published in 1993 by Zippel, Voigt, Knaust and Luan in the Journal of Comparative Physiology A. The researchers trained goldfish to tell apart two amino acid odours, which is to say two smells. It did not take long. Ten to twenty rewards were enough for the fish to learn the difference.

Then came the test of how long the learning lasted. The long-term memory of that smell discrimination held for at least three months. That is a very long way from three seconds.

A second study points the same way, and it looks at timing rather than smell. At the University of Plymouth, Gee, Stephenson and Wright published a study in 1994 in the Journal of the Experimental Analysis of Behavior. Goldfish were trained to press a lever for food. The researchers then cut the period in which the lever delivered food to one hour in every 24, at the same time each day.

The fish adjusted. Their lever pressing became concentrated around that feeding hour, as though in anticipation of feeding time. An animal that forgot everything within seconds could not have done that. It had to carry something about the daily schedule from one day to the next.

So why does the myth survive? Culum Brown, a fish cognition researcher at Macquarie University, has a suspicion that he shared with Live Science. He thinks the story persists partly because it makes people feel better about keeping goldfish in tiny bowls or small tanks. If the fish forgets each moment, a bare bowl hardly seems to matter.