Color perception: characteristics, functioning and alterations

Although it may seem objective, color is a private perceptual experience and therefore subjective (just like the perception of pain). But... What does the perception of color imply? What does it depend on that we perceive some colors and others? What makes us perceive a red, a blue or a yellow?

In this article we will talk about how colors are perceived, different colors and pathologies associated with the perception of color, among other topics.

• Related article: "Color psychology: meaning and curiosities of colors"

What is the color?

There are different definitions for color. Color can be understood as a perceptual response to objects and lights that gives them certain qualities (such as green). It can also be considered a characteristic of the perceptual response.

To define colors, in our day to day we usually use examples (such as "blue is like the sea", "green is like trees" or "black is like darkness".

Factors that determine color perception

There are four important factors when it comes to perceiving colors. These are:

• Wavelength and illumination: that is, how objects reflect light.
• The effect of the surrounding area: also called simultaneous contrast.
• The level of adaptation of the observer: presence of light or darkness (the darker, the more we perceive blue [short wavelength]).
• The memory of color: knowledge of the characteristic color of certain objects influences our perception.

Color consistency

On the other hand, the constancy of color also plays a key role in the perception of color; This implies that we perceive colors "always" the same (in natural conditions), that is, red for us will always be red, for example.

In any case, this constancy is partial, since color perception changes a bit when lighting changes.

How do we perceive colors?

The colors that we perceive are the result of the mixture of the wavelengths reflected by the objects; we can say that the light is filtered by the surface on which it falls. There are three types of wavelengths:

• Short wave: blue color.
• Medium wave: green color.
• Long wave: red color.

The remaining colors (other than these three) result from the mixing of these three wavelengths.

The perceptual process

Visual perception is determined by neural processing in all stages of the visual system. This depends on the cones, among other variables.

At a physiological level, there is a selective discoloration of visual pigments in color adaptation. This involves specific neurons in a specific area of ​​the brain, area V4, located in the extrastriate cortex (secondary visual cortex).

Striated neurons respond to visual stimulus; this answer is related to wavelength (which determines the type of color we see), and the response of the V4 neurons is related to perception.

Color types

There are two types of colors:

1. Achromatic

These colors have no hue; it's about black, white, and grays. At the cerebral level and from sight, we perceive achromatic colors with rods (receptors), which are photoreceptor cells in the retina responsible for vision in low light conditions.

2. Chromatic

Chromatic colors have nuance: they are all "other colors", such as blue, red, green... Unlike the previous ones, the receptors for these colors are the cones (photosensitive cells that are located in the retina, responsible for us to perceive colors in one way or another).

Color perception functions

The perception of color has a number of functions for humans, but also for some animals (since not all see in color). Let's get to know them:

1. Adaptive

Perceiving colors implies survival value, and therefore an adaptive value, since it allows: searching for food, detecting dangers and interpreting emotions.

The perception of color results from an evolutionary development (for example, the fact of detecting fruit between the foliage, increases the probability that that animal has food, eats, and therefore survive).

2. Esthetic

The fact of perceiving colors implies being able to appreciate beauty and aesthetics, as well as appreciate the nuances of objects, landscapes, art (for example in pictures), of people, etc.

3. Perceptual organization

Perceiving the different colors allows you to organize the world by separate areas or segments.

Associated vision pathologies

The basic alteration of color perception is color blindness. This alteration implies that the person sees some different colors to the rest of the people, and "confuses" or interchanges some of them, or that he sees directly in black and white.

It is an alteration of genetic origin in the ability to distinguish colors, which affects 8% of men and 1% of women (because it is recessive linked to sex). Two types are known:

1. Monochromatism

The first type of color blindness is about a rare form of color blindness (total color blindness), manifested in 10 people out of a million. Affected people do not have functional cones, that is, they show vision only with rods; come in white, black and gray. On the other hand, they need protection from sunlight.

2. Dichromatism

The other type of color blindness involves blindness to some colors. It is linked to sex, and three subtypes are known: protanopia, deuteranopia and tritanopia.

Deuteranopia

It is the absence of retinal photoreceptors of the green color (medium waves). They see the same colors but with a different neutral point.

Protanopia

It is the total absence of retinal photoreceptors of the red color (long waves).

Tritanopia

It is a very rare condition in which the retinal photoreceptors of the blue color (short waves) are absent. This is very rare.

Bibliographic references:

• Monserrat, J. (1998). Visual perception. New Library Psychology University. Madrid
• Goldstein, E.B. (2006). Sensation and perception. 6th edition. Debate. Madrid
• Manzanero, A. Perception psychology. Complutense University of Madrid (UCM)