How they see
How does a goldfish see the world?
Sees ultraviolet and red alike
The humble goldfish, circling its bowl, quietly outdoes us in colour. A true tetrachromat, it sees not only the reds, greens and blues we know but ultraviolet too, a fourth dimension of colour layered over the familiar. Its watery world is likely more vivid and varied than anything its owner perceives.
See through their eyes
Human ≈ 60 cpd (20/10)
How sharp is a goldfish's vision?
Its eyes resolve about 2 cycles per degree (20/300), while a human reaches around 60 cpd (20/10). Its field of view spans about 340°.
How does a goldfish see a human?
Its eyes resolve about 2 cycles per degree against your 60, so a face has to be roughly 30 times closer for it to pick out the detail you do. Your outline and your movement read clearly; your expression does not.
Colour comparison
How each colour shifts when seen through this animal's eyes, using the same colour model as the app. Tones a screen can't emit (such as ultraviolet) are shown as an approximation.
What colours can a goldfish see?
Full four-dimensional colour from ultraviolet to red.
Photoreceptors
Tetrachromat (4 cones), including UV
Cone peak sensitivities
- UV356 nm
- S (blue)447 nm
- M (green)537 nm
- L (red)620 nm
How does a goldfish see in the dark?
Moderate.
How does a goldfish's vision compare to a human's?
A goldfish's detail, about 20/300, is far below your 20/20. In colour it beats you outright: a full four primary colours to your three, adding ultraviolet at one end and reaching well into red at the other.
What is special about a goldfish's vision?
- Sees ultraviolet and red
- Classic colour-vision model animal
- Near-panoramic field
What the research shows
The goldfish became a model animal because its colour vision has been confirmed from several independent directions. Palacios et al. (1998) recorded from single cones with suction electrodes and found four classes peaking near 356, 447, 537 and 623 nm (the chart on this page rounds the last to 620 nm), values that agree with earlier microspectrophotometry by Bowmaker et al. (1991). Goldfish pigments are built largely on the A2 form of retinal, which shifts sensitivity towards longer wavelengths, so exact peaks depend on the chromophore mix. Cell recordings cannot prove that a channel is used, which is why Neumeyer (1992) matters: goldfish discriminated ultraviolet wavelengths behaviourally, showing that the UV cone contributes to colour vision.
Acuity was also measured behaviourally. Neumeyer (2003) used a two-choice task and found a maximum of about 2.0 cpd in light between 446 and 683 nm, with lower values in the ultraviolet. The page uses that 2 cpd, roughly 20/300. Flicker fusion, estimated at 30–70 Hz, depends on water temperature because the fish is an ectotherm, so no single value fits every tank. On a screen the ultraviolet dimension cannot be shown at all, since a phone camera filters UV out and a display has no UV primary, and a four-cone colour space cannot be compressed into three primaries without losing distinctions the fish can make.
Guides: Animals that see ultraviolet · Which animal has the best eyesight? · All guides
Scientific sources
- Neumeyer (1992)
- Bowmaker (1998)
- Neumeyer (2003)
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