How do scientists know?

[babybop6379]

how do scientists know that certain animals can only see in black and white , some see colour and so on? the animal cant say nowt so how do they know?

[Avatar]

They sit the animal in front of both a colour telly and a black and white telly and see which one it watches most.
Or, they examine the eyes of a dead specimen, if it has more rods than cones (might be vice versa) then the animal wil be less sensitive to colours)
Also probably by experimentation in labs, by using colours with the same grey tonality but which are different colours and trying to train the animal to select a certain colour for a food reward.
My theory anyway.

[Peter Pedant]

In the sense we know something....

that is one does an experiment - or make an observation
and then draw conclusions from it...

FOr example in a dead bird (nothing live here) you can show that some lignt sensitive cells have a glob of coloured fat at the bottom

from this one can conclude that the globule filters the colour and that it is functioning as a colour sensitive cell.
[you may comment ah but they dont KNOW do they? and I regard this as more of a philosophical q that I cant discuss, on this lines of how can we know anything of the outside world]

IF a retina of a dead animal - see above - has two different kinds of light sensitive cells (such as A and B or rods and cones) It is reasonable to conclude that they differ in structure and so they differ in function.
and then one can plan other eexperimients to see how they differ - such as seeing the responses to different coloured light.

Slow I know \- but the colour vision theory has developed over 200 years. First mooted by bug-eyed John Dalton of atomic theory fame.

Bug eyed because I think he was the one who inserted a circular wire with a little ball on the end
in and around the back of his eye
uuuuuuugh !
not only when he went dink dink on it
the ball caused a circular defect in hisfield of vision
uuuuuuugh !
but not only that
butwhen he looked far and near
the field size did NOT change size
uuuuuugh!!!
from THIS he concluded that the eye muscles did not have a part to play in accommodation (looking far and near)
but that theydid something else
(rotate the eyeball)
uuuuuuuuugh!!
and he did this in 1802 I think


so wow! we dont do this sort of thing nowadays !

[Noweia]

By looking at the cells in the eyes - an animal with no eye cells that can tell the difference between colours will not have color vision.