Are Fishes as Forgetful as We Think?
“Excuse my fish brain” and “I’ve got the memory of a goldfish” are sayings commonly used to express being extremely forgetful -- fish are generalised as having small brains and therefore supposedly low intelligence and short memory spans. But studies have found this to be untrue, fishes who were taught specific tasks such as favouring certain objects or how to escape a trap remembered and could still complete the tasks months later.
One study tested goldfishes’ long term memory by training them to navigate a maze using treats as positive reinforcement and letting them rest for up to six months, then seeing if they still remembered how to navigate the maze. It was found that the fishes were often quicker to navigate the maze after the resting period than they were the last time they had trained months previously, indicating a strong long term memory.
For example, cleaner wrasses, small fish that cleans food debris and other parasites off of bigger fish, are suspected to be able to recognise more than 100 individual client fish of various species. They have been observed to prioritise clients that they have seen less recently as well as choosing who to tend to first between regular clients and clients who they’ve not encountered before. This suggests that they are using memory along with 3 dimensions -- who, what and when -- to make such decisions. By doing this, fish demonstrate episodic memory, a skill held in high regard by biologists.
So the next time you hear someone using “fish brain” as a metaphor for their poor memory, you can bust that misconception with this new-found knowledge. The question is, can you remember it?
Written by Abi Foster