[SquarishTriangle (OP)]

I see blue (460nm), and I know to call it blue; that's what I've been taught to call that particular colour all those years ago.

Joe Blogs (he's up to speed in the technosphere) sees blue (460nm), and he knows to call it blue because he also has been taught to put that particular name to what he perceives as that particular colour.

The same wavelength, the same name. Yet as I can't see what he sees, how do I know if we are perceiving the same 'colour'? The only way I can describe the colour 460nm to Mr Blogs is to say it's name, or perhaps how I feel about it (but that is not very helpful). How can you show that the world appears to one person colourwise in the same way as it does to the next?

[neilep]

Hi Squarish Triangle,

Welcome to the site.

Great question..in fact a fantastic most enlightened brilliant question.

here is the same question asked by someone here before and the link to the thread.


http://www.thenakedscientists.com/forum/topic.asp?TOPIC_ID=689

Enjoy the site.

[Karen W.]

I know nothing about this topic, just postin to say welcome to the forum! I hope you like it enough to stay around! Nice to have you on board!

[eric l]

There is a very good article on colour perception in Wikipedia.  I have referred to it so often that I should know the link by heart, but I still had to check.  So here it is
http://en.wikipedia.org/wiki/Colour_perception [Links inactive - To make links active and clickable, login or click here to register]
What it amounts to is that in your retina you have luminosity sensors (the rods) and colour sensors (the cones).  There are three types of cones, with different sensitivity regarding the wavelength.  Now if you and Joe Blogs do not have the same ratios for the three types of cones, it may well be that the input in your brain for the same wavelength is not the same for you and for Joe, the more so when the colour you perceive is not monochromatic (single wavelength).
Colour blindness is almost alway due to the absence of one type of cones.

[Soul Surfer]

In a strictly logical and philosophical discussion you are correct and I cannot prove that my perception of colour is the same as yours.  But language isn't as simple as that.  You have already pointed out that the expressions and names of colours are learned and agreed upon and only cause problems where small differences or colour blindness intervenes.  There are also other qualities like  "warmth"  "coolness" "brightness" and "dullness" etc  associated with colours and these can produce an independent level of agreement between most people  although individuals have striking differences in the colours that they like best.
Human language is NOT a precise scientific communication process but a way of finding and developing common ground and understanding.  The big problems always come when people do not trust each other and look for small loopholes in what they say.  These always exist and can be used as a good excuse for non communication.

[daveshorts]

Aparently whether you can tell two colours apart when shown them one at a time is very related to whether you have two different names for them. eg if you only had the word purple you would have difficulty telling it apart from something mauve shown to you afterwards. If you are directly comparing it doesn't make any difference though - so whether this is a difference in experience or just filing is possibly philisophical.

Some of the work on this was done on tribes in Papua New Guinea ? who had loads of words for greens and browns but not for blue. As blue was not very important to them.

[science_guy]

As blue was not very important to them.

It would seem that they dont see somthing as very important if they are forced to strain their poor necks to look at it []

[daveshorts]

If you live in a rainforest the sky is rarely seen and even more rarely blue. I guess they have a word for sky, but not blue.

[Heliotrope]

I was listening to a podcast that was discussing a similar thing.
Apparently, if I'm remembering this correctly, some cultures don't separate the colours in the same way we do.
I say "we" there and what I mean is a relatively advanced technological society as compared to a non-technological society.
It seems that the more technologically advanced a society is the more divisions in it's colour descriptions it can define.
Some cultures call something red and what they mean is that the thing they call red may stretch from a sort of pink to a brownish hue with only a couple of divisions to make separate colours disctinctly discribable.
Whereas we would have 60 different types of red for example, they might have only 4.

[eric l]

I do have an experience about how persons can have a different perception of the same colour.
Some years ago I worked in a team on a project involving colours and colour measurement.  Everyone could agree on how the usual colours had to be named, but it got quite difficult when it came to shades.  For example :  we had a colour that we called "Bianchi green" because it was the colour of the frame of the Bianchi racing bicycles (a lot of us were involved directly or indirectly in cycling).  It is a kind of blueish green.  One member of the team however insisted on calling it "Bianchi blue".  In the following discussions he claimed that to him it was closer to "unspecified blue" or "standard blue" than to "unspecified green" or "standard green".  It ended by us making tiles with shades from yellow over green and blue to violet, over 50 tiles in all.  Then we asked each member of the team - and later also colleagues from other teams - to select "standard green" and "standard blue".  With a population of something between 40 and 50 persons in the test, a different shades were indicated as "standard green" and three (other) shades as "standard blue" (or the other way around, it was never reported because in the project we used CIE Lab data rather than names of colours - we just had involved other people out of curiosity).