Can any animals see beyond an octave of light?


Throwing out a question to the community:
The average range of human hearing is between 20 Hz and 20,000 Hz, covering a maximum of 10 octaves. Though not all that range sounds “musical,” we hear an obvious, salient and special relationship between two notes an octave or two apart, to the extent that they often sound like a single note (what with overtones and all).

The visible spectrum of light is between 390 to 700 nm (430–770 THz), or a little less than one octave. I used to think that the blending of colors between violet and red represents bandwidths approaching an octave. From what I understand that’s not true; it’s more an effect of how our retinas and brains process color information.

But I’ve always wondered what it would be like to “see an octave of light.” Would that overtone effect cause problems in color perception? Would it confer any advantages or disadvantages? And are there any animals that have been found to respond to more than an octave of light?


I don’t know about the overall range, but some insects can see into the ultraviolet. Many flowers that look drab to us stand out like beacons in the UV range to attract pollinators. Pit vipers such as rattlesnakes “see” infrared, but I don’t know how, or if, that is integrated with their vision

Cats and wizards, we are told, can see octarine. It wouldn’t surprise me if octopuses can also.


Some people can as well. It is speculated that Claude Monet was one of those people.


But wouldn’t it be impossible to verify?

A1: Hey look, an ultraviolet sofa!
A2: It’s purple.
A1: No, look, it’s beyond purple, it’s ultraviolet.
A2: Oh, you mean a kind of bluish-purple.
A1: No, it’s ultraviolet.
A2: Have it your way, indigo is now called ultraviolet…


I don’t know about the sense of “seemingly repeated” but in terms of brightness I think octaves are akin to f-stops. As far as color hue perception goes I think the scale is more linear.

So doubling a note’s frequency makes it seem the same note, only higher.

Doubling a scene’s brightness makes it seem “the next notch up” in brightness.

With hues there isn’t much opportunity to double or halve the frequency and still stay within the visible range. So your question is, I think, if we had wider perception would doubling a frequency bring us to the same color again, only “elevated” in some what that’s hard to describe?



It’s been verified through lab tests that ultraviolet vision is sometimes a side effect of cataract surgery. Whether or not Claude Monet developed this ability after his surgery is speculation, because he was never tested for this, but he definitely changed the color schemes he painted with.


I don’t think overtones are applicable here. If you think about how we generate sound, it is usually with a vibrating string or column of air, where multiples of the basic wavelength naturally fit. Most visible light on the other hand either comes from electrons jumping between different energy levels in molecules (including near ultraviolet) or molecules switching between different levels of vibration (including near infrared).

You do get something like overtones from that, but partly because it involves transitions and even more because the underlying system isn’t linear, they don’t form a harmonic series. The hydrogen spectral series is an example; at best it’s like overtones on a drum. So exact integers ratios aren’t common, and in the end we don’t pick up the specific frequencies like we do with sound anyway, just which of our visual pigments are capable of absorbing them. It’s not even a linear scale, it’s done by buckets.

As has been said, lots of animals respond to frequencies beyond what we see, but not by much. Many insects see ultraviolet, but only near ultraviolet within about 300 nm, and then they generally don’t see red. Likewise rattlesnakes famously see infrared, but that doesn’t mean a larger range – I couldn’t find much on them, but a little summary here lists them as “different” rather than “more”.

Birds do better, as many can see both red and ultraviolet; here is a paper exploring their color space that I found interesting. While many marine fish see only blue colors, there are some like damselfish that have this same kind of expanded range. Some freshwater fish apparently see near infrared to about 900 nm, but I’m not sure if any can see that and near ultraviolet. In any case, that means that some of the vertebrates make it a full octave range and maybe a little bit more, though not by too much.

Mostly I think advantages or disadvantages would apply to different frequencies more than the total range. For instance ultraviolet is potentially harmful not to screen out but lets you see markings on flowers, or stripes on other damselfish, hidden to animals like us. But I guess you could say it gives them more of opportunities for visual signals to one other, if they are able to produce the colors somehow, as studied in the bird paper.

For all their wonders, octopuses are said not to have color vision. It used to be considered that color wasn’t much use in the ocean in anyway, since past a few meters down all the ambient light is blue. However, it’s been discovered many fish are exceptions that see things like the fainter fluorescent colors down there. So maybe some cephalopods have developed the same, but it’s not really what you expect from them; they pick up on things like the polarization of light instead.

For the record most people don’t see ultraviolet as purple, they see it as nothing, because our eyes filter it out. So you could tell if someone can respond to it or not. Things like black lights will look purple only because they aren’t actually monochromatic, and you see the little bit that makes it into your visible range.


This is a question that has fascinated many of us for a long time. There is an epic Radio Lab episode which describes the Mantis Shrimp. It may be able to see something like 17 primary colors, but current research can’t prove it. (When you have a couple free hours, start googling it. I guarantee you will be entertained)


Write something rude on the couch with ultraviolet ink and see who blushes.


I don’t think it would, because though sounds of different frequencies are perceived via the same apparatus, light of different frequencies is perceived via different cells.

Cone cells have relatively narrow frequency responses. Humans (usually) have three types of cone cells:

Whereas birds have 4, enabling them to see UV.


Alas, cephalopods are monochromats.
[Buggrit, chenille got there first]


But the de-lensed observers just experience that UV light as violet (because the UV photons are stimulating the same cones as violet light does – the S-cones, and some response from L-cones).


[Edit: I see that the conversation pretty much covered this already - I’ll leave this post up for the anecdotes, and also for the general principle of not deleting parts of conversational record without good cause.]

As I understand it, anyone that’s had lens removal for cateracts (like Monet did) can see at least more UV, as the eye’s lens has a filter.

I recall that it’s one of the things that the better ‘so you’re​ having cateract removal’ information sites touch on - I spent some time digging such info up some years back for my then (and sadly missed) mother-in-law, pre-cateract operation.

And while I never did manage to get her to try using a UV ID marker light as a torch (:wink:), she noted that there was a difference (including previously colour balanced replacement teeth suddenly standing as significantly-no-longer-colour-matching).

It’d be interesting to get anyone who’s had the op. to do some more controlled experimenting to see how much additional UV light gets passed this way - and whether ‘the octave’ is actually passed.

(I’m sure the research will have been done somewhere, but I no longer have Athens/Shibboleth access. :/)


What, they’re going to force Beschizza to read the headlines before he double-posts?



OH. I thought you said “ultraviolent.”


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