The idea that a goldfish forgets everything within three seconds is a myth. Goldfish hold onto what they learn for months.1Discover Wildlife. Do goldfish really only have a 3 second memory? Their memory also isn’t a single thing: they remember places, colours, times of day and unpleasant experiences, much as other animals do.
How Long Goldfish Memories Actually Last
Goldfish can keep a learned memory for at least three months.2Discover Wildlife. Do goldfish really only have a 3 second memory? In one reported case, lab goldfish were trained to pick a tube of a certain colour to get food, then went a full year without seeing the tubes. When the tubes came back, the fish chose the right colour straight away.3howfishbehave.ca. Long-term memory in fishes The year-long case is one lab’s observation, not an average for all goldfish.
In a home tank, remembering looks like a fish rushing to the front at the usual feeding spot, which is recalling a routine. Fish that ignore one person but greet the feeder are showing a learned link. A fish that keeps hiding after being netted may recall the bad experience, though stress or illness can also cause hiding.
A goldfish gliding past the same plant with no reaction looks forgetful, but it is usually just ignoring something harmless. A fish often approaches or startles at a new object, which suggests it remembers what was there before.
It also helps to tell memory apart from reacting in the moment. A fish that darts to the glass when a hand appears over the tank might just be responding to a shape and shadow right now. Memory shows up when behaviour depends on the past, such as gathering at one corner at feeding time even when no one is near, or behaving differently toward the person who feeds it than toward a stranger.
What Goldfish Remember
Goldfish can learn to swim through a maze to reach food.4PubMed Central. Spatial Cognition in Teleost Fish: Strategies and Mechanisms Some learn a fixed body turn, such as always turning right, to find it. Others learn where the food is by using landmarks around the room, and they get lost when those landmarks are hidden. Goldfish can use both methods and switch between them depending on what information is available.5PubMed Central. Spatial Cognition in Teleost Fish: Strategies and Mechanisms Overall they tend to rely on landmarks, as killifish and Siamese fighting fish do, and they learn mazes faster than zebrafish.6PubMed. Place versus response learning in fish: a comparison between species
At home, this means moving the tank or rearranging decor can briefly confuse a fish that uses landmarks. Fish may even track a window or lamp outside the glass as reference points. After big changes, give a fish a few days to relearn before worrying.
Goldfish also keep track of time. They can learn how long to wait between a signal and what follows it, getting most active right when the event is due.7PubMed. Temporal control of conditioned responding in goldfish. Goldfish fed at the same time each day start getting active before the food arrives,8PubMed. Influence of light on feeding anticipatory activity in goldfish because they have an internal clock that sets itself to regular feeding times and is affected by light.9PubMed. Influence of light on feeding anticipatory activity in goldfish Feeding time even helps keep a goldfish’s body clocks in sync, as it does in mammals.10PubMed Central. Circadian clock genes of goldfish, Carassius auratus: cDNA cloning and rhythmic expression of Period and Cryptochrome transcripts in retina, liver, and gut If the schedule changes, the habit fades and shifts, then rebuilds around the new time.
Fish can also learn and remember negative experiences.11PubMed Central. Fish Welfare in Public Aquariums and Zoological Collections Goldfish can learn to avoid a mild unpleasant stimulus that follows a warning light.12PubMed Central. Avoidance response in goldfish: emotional and temporal involvement of medial and lateral telencephalic pallium
Whether goldfish learn by watching each other is less settled. Goldfish that watched a trained fish run a maze learned it more slowly than fish that didn’t watch. But the watchers were quicker to accept the food reward, so they picked up something.13PubMed. The effect of observing trained conspecifics on the performance and motivation of goldfish, Carassius auratus, in a spatial task Copying routes from tankmates isn’t clearly proven, so train each fish directly.
How to Train Your Goldfish
Goldfish can be trained.14Discover Wildlife. Do goldfish really only have a 3 second memory? They link a cue, like a colour, with food and keep that link for months.15howfishbehave.ca. Long-term memory in fishes
A simple first trick is coming to a coloured target. Hold a small coloured object at the same spot just before feeding, and drop a pellet only when the fish swims to it. Repeat once or twice daily for several days, until the fish approaches before the food appears. Then move the target slowly to teach following.
Routine helps too. Feed at the same times, and pair a tap or light with meals as a clear signal. Keep that signal identical each time.
A few mistakes slow things down. Overfeeding during training fouls the water and dulls interest in rewards. Changing cues often confuses the fish. Expecting results in one session doesn’t work, since learning builds over days. And frightening the fish creates avoidance memories that last too.
Fancy goldfish may learn more slowly than common goldfish, given the smaller brains described below. Progress lost after a break usually returns quickly.
What Helps or Harms a Goldfish’s Memory
Goldfish memory for places relies on the forebrain, the front of the brain.16PubMed. Lateral and medial telencephalic pallium lesions impair spatial memory in goldfish One part of it handles emotional memories, much like the mammal amygdala, and another handles places and timing, much like the hippocampus.17PubMed Central. Avoidance response in goldfish: emotional and temporal involvement of medial and lateral telencephalic pallium Damage to the timing area stops goldfish linking events separated by a gap, while simpler links survive.18PubMed. Trace classical conditioning impairment after lesion of the lateral part of the goldfish telencephalic pallium suggests a long ancestry of the episodic memory function of the vertebrate hippocampus Blocking a key brain receptor stops goldfish learning new places but doesn’t erase places already learned.19PubMed. Spatial learning and goldfish telencephalon NMDA receptors
The tank itself matters. Goldfish kept in tanks with objects to explore and room to exercise learned a maze faster than those in bare tanks, and they grew more new cells in the front of the brain.20PubMed Central. Small-scale environmental enrichment and exercise enhance learning and spatial memory of Carassius auratus, and increase cell proliferation in the telencephalon: an exploratory study
Turning a bare bowl into an enriching tank starts with size: bowls are too small, and a filtered tank of generous size suits goldfish. Add plants, smooth rocks and caves to explore. Rotate one or two items occasionally rather than moving everything at once.
Breeding matters as well. Fancy, highly bred goldfish have much smaller brains than common goldfish, especially in the front of the brain.21PubMed Central. Goldfish phenomics reveals commonalities and a lack of universality in the domestication process for ornamentation Common and comet types are closer to the wild form, while fancy types still learn, just perhaps less readily.
Water contaminants can impair learning too. Caffeine in the water stopped goldfish learning a maze,22BIOS. The effects of caffeine and sertraline on spatial learning in goldfish, Carassius auratus (Cypriniformes: Cyprinidae) and the antidepressant sertraline weakened maze learning.23BIOS. The effects of caffeine and sertraline on spatial learning in goldfish, Carassius auratus (Cypriniformes: Cyprinidae) The pesticide parathion, at levels found in the environment, can disrupt learning and memory.24Environmental Pollution Series A, Ecological and Biological. The effects of parathion on acquisition and retention of shuttlebox avoidance-conditioning in the goldfish Carassius auratus So keep tank water free of household chemicals and medicines, and use dechlorinated water.