How long is a goldfish’s memory?

There is a popular belief that goldfish only have a 3 second memory. But, the humble goldfish may not only have a longer memory than most people think, but may also be far smarter.

If you own a goldfish there’s a good chance it remembers you for longer than 3 seconds. Image by Benson Kua via Flickr

How long can goldfish remember?

Quite a simple experiment conducted by a 15-year-old school boy debunked the theory that goldfish don’t remember longer than a few seconds. When he would feed his pet goldfish he would put a red piece of Lego in their fish tank, and would sprinkle food around the Lego block. At first the fish seemed scared of the block, but after a couple weeks the goldfish learned that the red block meant that food was coming, and would swim straight towards it.

After the goldfish seemed to learn what the block meant, he then stopped using the Lego piece for 1 week. He then re-introduced the block, and the fish swam straight towards it in anticipation of food.

This quite elegant experiment shows that goldfish can remember information for at least a week.

In another experiment researchers trained young goldfish by playing a certain sound during feeding time. These goldfish were then released into the ocean. About 6 months later the researchers played the sound again over a loudspeaker and many of the goldfish returned to where the sound was playing. Again much longer than the 3 second myth would have you believe.

So, a goldfish clearly can remember things for longer than 3 seconds, but are they at all smart?

How smart are goldfish?

If I asked you to name a ‘smart’ animal you would probably say something like a dolphin or a chimpanzee, I definitely don’t think you would say a type of fish. However, scientists think that many fish are smarter than we give credit for.

Many biologists think that fish are actually quite intelligent. A biologist from the University of Edinburgh says that “in many areas, such as memory, the cognitive powers [of fish] match or exceed those of higher vertebrates, including nonhuman primates”

Goldfish have shown that they have an ability to learn and process information. Pet goldfish can distinguish between humans, and often recognise the human that regularly feeds them. Pet goldfish can also seem quite scared of new people, but become more comfortable with their owners over time as they realise they aren’t a threat.

Goldfish have also been taught to do relatively complex tasks like swimming through mazes, or pushing a ball into a net. This means that goldfish not only have the ability to recall information, such as its owner that feeds it, but also has the capacity for more complex processing and cognition.

They may not look smart but goldfish have been trained to perform quite complex tasks. Image by Gexydaf via Flickr

Why do we think that goldfish are dumb?

Many people have this pre-conceived notion that evolution is liner, that fish evolved into reptiles, that evolved into mammals, then primates and then us. So, fish much be less intelligent than all animals that came after it, right? But that’s not really how evolution works. Yes, 400 million years ago there was a prehistoric fish that crawled out of water, which over millions of years eventually evolved in humans. But, fish are not the same as they were 400 million years ago.

Scientists think that fish have evolved over millions of years to remember things like where they can find food, and what a predator does and doesn’t look like – in the same way they recognise their owner is not a threat and will give them food.

So, we really should give goldfish more credit. While they’re definitely not the smartest creatures in the animal kingdom, goldfish are definitely more intelligent than the 3 second memory myth gives them credit for.


2 Responses to “How long is a goldfish’s memory?”

  1. Alastair Saunders says:

    Very good point. I guess its hard to test actual memory in goldfish

  2. Ann says:

    This experiment makes the goldfish to build a conditioned reflex. I wonder if the formation of a conditioned reflex suggests a formation of memory?