Goldfish May Have Longer Memories Than Just Three Seconds

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It’s a common adage — to have a “memory like a goldfish” is to be absolutely absent-minded. Though they’re beloved by many as household pets, goldfish (Carassius auratus) are known for having a memory that lasts just three seconds. 

Yet despite that forgetful reputation, scientists have known for decades that such claims don’t hold up to scrutiny. The freshwater fish are much smarter than you might think, and studies have repeatedly shown that their memories can actually span several months.  

What’s more, a recent surge in research on fish brain function has found that goldfish share many of the same cognitive abilities as humans, including object perception, social learning, and spatial awareness. 

Goldfish and Memory Span Misconceptions 

The key brain structure that allows mammals to form memories — the hippocampus — is absent in fish. In many animals with higher-level brain function, the hippocampus stores explicit memory, which allows us to consciously recall specific facts and firsthand experiences.  

For years, many pet owners believed that the lack of a hippocampus meant goldfish didn’t have the ability to store memories at all, leading to the rise of the three-second memory myth.  

“I think the misconception comes, basically, from the fact that a lot of people — and I hope less and less — maintain fish in a circular bowl,” says behavioral ecologist Adelaide Sibeaux, who researches navigation in animals at the University of Oxford. “We haven’t been giving fish [the chance] to just show us how smart they are.” 

However, research conducted as early as the 1960s proved that goldfish do, in fact, have much longer memories than a mere three seconds. In 1966, scientists at the University of Michigan conducted a study showing that goldfish improved at a shock-avoidance exercise over the course of multiple trials and multiple days, providing early evidence of short-term memory formation.  

Since then, scientists have consistently succeeded in training goldfish on memory- and perception-related exercises, teaching them to do everything from recognizing human faces to even driving a makeshift robotic car.  

These skills may seem basic, but for researchers, they provide evidence that goldfish are able to connect events and objects at different points in time — a key indicator of explicit memory.  

Read More: How Intelligence Is Measured In The Animal Kingdom

A Wave of Research on Goldfish Cognition   

In the past ten years, in particular, there’s been a surge in studies on fish cognition, as researchers seek clues to human evolution hidden in the brains of our aquatic predecessors.  

Most recently, in a 2022 study, Sibeaux and her colleagues at the University of Oxford found that goldfish have the ability to estimate distance, further proving their intelligence. Researchers trained goldfish to swim a set distance through a tank lined with vertical stripes, and tracked how their swimming pattern changed if they altered the pattern of these stripes.  

Based on these results, researchers concluded that goldfish are able to navigate their surroundings and remember visual cues through a process known as optic flow, estimating distance by tracking the motion of objects around them. 

According to Sibeaux, these results could position goldfish “as a model system to investigate the evolution of the mechanisms that underpin spatial cognition in vertebrates.” In other words, while goldfish may not have the ability to remember and process their surroundings in the same way that humans do, they’re still able to perform these cognitive functions at a much higher level than previously thought.  

In another 2022 study, published in the journal Animals, scientists showed that goldfish were able to distinguish between photographs of plastic turtles and plastic frogs. The process of object constancy — the ability to recognize different objects from different angles — is another key indicator that goldfish might be smarter than we think.  

Read More: Can Fish Recognize Themselves? These Cleaner Wrasses Passed the Mirror Test

What We Don’t Know About Memory in Goldfish

The biggest mystery that remains, though, is which part of the brain goldfish use to store memory and process their surroundings. While fish don’t have a hippocampus, they do have a similar region of the brain known as the pallium, which some researchers say helps them connect events at different points in time and space. 

But recent studies have split on which part of the pallium is responsible for storing spatial memory. As recently as late 2023, scientists found that goldfish with lesions in the pallium performed worse on memory tasks than those without lesions, regardless of which part was altered. The study suggests that goldfish may use both parts of the pallium for memory, challenging the previous assumption that just one part is involved. 

As researchers continue to investigate, one thing is certain: there’s more to these popular pets than meets the eye — and their unexpectedly advanced memory could provide clues to how the human brain has evolved over time. 

“There is a lot of change happening at the moment — among humans also, like global change,” says Sibeaux. “If you understand better how we navigate, how we function, then we can also understand if (fish) do have the ability to cope with those changes.”  

Read More: 5 of the World’s Most Intelligent Animals

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