THE ANIMAL FILES

Goldfish

Carassius auratus

A familiar fish with a learnable world.

Goldfish have a long history of selective breeding. Their colour vision includes ultraviolet-sensitive cones, and they can learn associations between signals and feeding.[1]

Follow the evidence ↓
Goldfish
Image: No machine-readable author provided. Heptagon assumed (based on copyright claims). · Commons · Public domain
Breeding history
Color forms developed through selection[1]
Vision
Several cone types, including ultraviolet sensitivity[1]
Learning
Associates repeated signals with food[1]

Color shaped by people

Goldfish were selectively bred for colour in China. People kept and bred preferred variants, eventually producing a wide range of colours, body shapes and fins. Their ornamental appearance reflects a long history of human selection.[1]

A color world unlike ours

Goldfish have four cone-cell classes with different spectral sensitivities, including ultraviolet. This is a statement about sensory equipment, not proof that a fish experiences color exactly as a human would imagine it. An environment can contain useful visual distinctions that do not match the ones most obvious to us.[1]

Repeated events can become expectations

Goldfish can associate visual signals with food and anticipate regularly scheduled feeding. These learned responses retain information beyond the instant a cue appears, contradicting the idea that every event is forgotten within seconds.[1]

A COMMON MIX-UP

Does a goldfish forget every event within seconds?

No. Recorded associative learning and responses to repeated cues require information to persist beyond an instant.[1]

TRY A LITTLE REASONING

Why might a fish approach before food actually enters the water?

Reveal the explanation

It may have learned a cue associated with feeding. Repeated observations are needed to distinguish such an association from a response to the food itself.[1]

Sources & editorial notes

Adapted and translated from the cited Wikipedia revisions, with source-linked reasoning. Image credit and licence are listed separately above.

Adapted and translated from Wikipedia contributors; exact revisions are linked below. CC BY-SA 4.0

  1. Wikipedia contributors — Carassius auratus (adapted and translated; exact revision)
  2. NCBI Taxonomy — Carassius auratus (identity and game lineage)

Last fact check:

One discovery leads to another

Common carpThe muddy mouthful is sorted before the meal is swallowed.Cyprinus carpio ↗Common breamA young bream does not yet have the deep body of a mature one.Abramis brama ↗Common roachA silvery shoaling fish changes its menu as it grows.Rutilus rutilus ↗