Sensory Perception

[Angrboda]

Regarding night vision.

This is not an educated opinion, so take it for what it's worth. The receptors in the human eye come in two basic kinds (IIRC), rods and cones. The cones, of which there are three types, detect color. (And I believe the most common color blindness is a defect with respect to the cones.) The rods on the other hand are purely black and white. However, the rods are more sensitive than the cones (in normal individuals), so in low light conditions, our vision is primarily black and white, as there is insufficient light to adequately stimulate the cones. If you have trouble seeing colors in low light, that just means you're normal. I don't know if there is any relationship between the defects which cause color blindness and the rods, so that part I don't know. I have also learned that there are people (well, at this point, one person), who has four different fully functional cone types. They can discern variations in color that normal three cone individuals can't. (And if I recall correctly, some color blindness results in 4 cone types, not all of which are functional).

Trivial fact. The retina where our peripheral vision is detected is extremely cone poor, so we see things at the periphery of our vision as largely black and white. However, our brains "fill in" the missing colors in our perceived perception so that we don't notice any change in color levels at the periphery.



(tetra-chromats)