On Jun 28, 5:20 pm,
na...@mips.inka.de (Christian Weisgerber) wrote:
> Peter Moylan <inva...@peter.pmoylan.org.invalid> wrote:
> > Most people don't even know that two colours can have completely
> > different spectra but be indistinguishable to human eyes. (For
> > physiological, not cultural, reasons.)
>
> It gets better: Identical spectra can also appear as different
> colors. For example, a white sheet of paper under an incandescent
> light should appear red--but it's still white, because there is
> some compensation for the spectrum of the ambient lighting going
> on.
>
Also, our minds interpret the electrical signals from our eyes, so
that, to some extent, we see what we expect to see. For example, if
you walk along a suburban street at dusk, where people in the houses
have switched on their (incandescent) lights, but not yet drawn the
curtains, the light in the rooms will look quite yellowish to someone
viewing it from outside, in the street. Because the person outside has
adapted their vision and perception to the more bluish daylight (or
the remains of daylight).
But the person inside the room has adapted their vision and perception
to the more yellowish incandescent ambient lighting. Viewing a sheet
of white paper inside the room, they will not see it as yellowish,
they will see it as white. Because they expect to see white, that is
what they see.
When Edwin Land was developing the Polaroid camera, he experimented
with only using two pigments (or two coloured filters for transmitted
light) instead of the more usual three. He found that people can be
induced to see colours that are not there. For example, if you project
a slide that includes a pattern that looks like grass, people will see
it as green, because that is what people expect grass to look like.
Grass is green, obviously. Even if there is no green light in the
projected image, because there are only red and blue filters.
Many years ago, I read "Eye and Brain" by RL Gregory, though I have
forgotten most of it. One of the aspects of "seeing" that this book
examines, is the considerable extent to which the brain processes and
interprets the raw data from the optic nerve, For example, we see the
world upside down, but our brain automatically corrects the image so
that we see the world the right way up. And there are many varieties
of optical illusion which work by tricking the brain into seeing
something which it expects to see, but which isn't actually there.
So I can well believe that people's ability to see, and to distinguish
certain colours, can be very much influenced by their cultural and
linguistic expectations, as per the TV programme which was mentioned
earlier.