What is the extent of a goldfish's memory?

Domesticated goldfish often don't receive the same level of care as other household pets. We frequently tap on their tanks without a second thought, neglect their living conditions, and when they pass away, they are often flushed away without ceremony. This starkly contrasts with how we would treat a beloved dog like Rover.

A common excuse for mistreating goldfish is the belief that they have no memory of their mistreatment. Many people claim that goldfish have extremely short memories—perhaps just three seconds—so they forget their surroundings with each lap around the bowl. But is this true? It seems unlikely that goldfish are perpetually surprised by the sight of the same castle in their tank.

This notion appears to be a myth. To debunk it, consider a study conducted at Israel's Technion Institute of Technology. Researchers spent a month training fish to associate an underwater bell with food. After being released into the sea and recaptured five months later, the fish still responded to the bell. This not only demonstrated their ability to learn but also proved their memories could last for months [source: Siegel-Itzkovich] [source: Simpson].

What about goldfish, in particular? Scientists at Plymouth University wanted to explore the learning and memory capabilities of goldfish. First, they trained goldfish to press a lever for food—a remarkable feat for a creature often underestimated. Over three months, the lever was active for only one hour each day. Instead of repeatedly pressing the lever without reward, the goldfish learned to reduce their attempts during non-reward times. They even gathered around the lever just before the feeding hour, showing they anticipated the upcoming meal [source: Standard].

In a separate study by Queen's University Belfast, researchers discovered that goldfish avoided areas of their tank where they had received electric shocks within the past 24 hours. This behavior suggests they retained memories of the painful experience [source: Highfield]. So, treat your goldfish with kindness—they remember more than you think.