Do fish really have a 3 second memory?

30 November 2015

Interview with

Kat Arney

You may have been told you have the memory of a goldfish during forgetful spells, but is this really such an insult? Kat Arney takes on another Mythconception...

Kat -  It's not clear where this myth originated, but it's often been used for comic effect, particularly by people whose memories aren't the best... What was I saying? There's even been a movie named after the supposed phenomenon - a romantic comedy rather than a fishy feature film.

In fact, most fish - including goldfish - are more than capable of performing pretty good feats of learning and memory, and anyone who has kept pet fish will know that they're not usually swimming about in a permanent state of freaked-out amnesia. And it's not hard to disprove either -  the claim has been debunked by many people; from university researchers and TV mythbusters to curious schoolkids.

For example, there's evidence that fish can distinguish colours, shapes, tastes and sounds. They may even recognise their owners, and certainly learn to become habituated to them, as well as other fish in their tank. And these memories last for months, not minutes.

According to a study by animal psychologists at Plymouth University, goldfish can even tell the time. The researchers trained the fish to nudge a lever to get food, but they fixed it so it only dispensed the goodies for one hour per day. The clever fish adapted quickly, learning to cluster around the lever as lunchtime approached.

Scientists are now trying to unpick the molecular nuts and bolts that underpin a goldfish's mind, by training them to respond to different coloured light cues associated with food.  And it's likely that the fundamental processes at the heart of a goldfish's mind are similar to those in ours, despite a few million years of evolutionary separation.

Furthermore, scientists have studied other fishy minds. At the Society for Experimental Biology annual meeting in 2014, a Canadian researcher presented data showing that African cichlids - small fish that are popular in domestic aquariums - can be trained to go to different parts of their tank to receive food. After three days of training, the fish were put into a different aquarium for 12 days. After that, they were popped back into the training arena, and showed a strong preference for seeking out the areas where they'd previously found yummy food. 

Of course, it makes little sense for animals like these fish to have virtually no capacity for making memories at all. In the wild they need to be able to remember the locations of safe places to eat free from the threat of predators, so while they're unlikely to win Mastermind any time soon, it's not surprising that they have a reasonable amount of brainpower. And, of course, any fish that can't remember the location of dinner aren't likely to do very well in evolutionary terms.

There's more. Scientists in Israel managed to train sea-dwelling fish to respond to particular sounds played over an underwater loudspeaker, coming towards the source of the sound and return for food. Importantly, they could remember their audio cue months later, flocking back for a feed when the sound was played again months later after living in the wild. There's more to this than a biological curiosity though. Many species of marine fish are farmed in large underwater pens, and this can have knock-on effects on their health and wellbeing. Perhaps a sonic signal, sent out to free-living fish that have previously been trained in captivity could be a good way of enticing them back to be caught,

Finally, perhaps my favourite fishy fact that I've discovered is this: goldfish can tell the difference between different types of music, according to a study from Japanese scientists. In their tests, fish were able to discriminate between the famous Toccata and Fugue in D minor by Johann Sebastian Bach - a piece of neatly precise organ music -  and Igor Stravinsky's effusive and orchestral Rite of Spring. Although the main finding was that they're not really fans of loud music at all, which isn't that surprising.

So next time someone makes a joke about goldfish having a tiny memory-span, you can remember that this is one myth that needs to be forgotten.

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